Download 1994 arctic ocean section - CCHDO - University of California San

The 1994
Arctic Ocean Section
The First Major Scientific Crossing
of the Arctic Ocean
1994 Arctic Ocean Section
— Historic Firsts —
• First U.S. and Canadian surface ships to reach the North Pole
• First surface ship crossing of the Arctic Ocean via the North Pole
• First circumnavigation of North America and Greenland by surface ships
• Northernmost rendezvous of three surface ships from the largest Arctic nations—Russia,
the U.S. and Canada—at 89°41′N, 011°24′E on August 23, 1994
— Significant Scientific Findings —
• Uncharted seamount discovered near 85°50′N, 166°00′E
• Atlantic layer of the Arctic Ocean found to be 0.5–1°C warmer than prior to 1993
• Large eddy of cold fresh shelf water found centered at 1000 m on the periphery of the
Makarov Basin
• Sediment observed on the ice from the Chukchi Sea to the North Pole
• Biological productivity estimated to be ten times greater than previous estimates
• Active microbial community found, indicating that bacteria and protists are significant consumers of plant production
• Mesozooplankton biomass found to increase with latitude
• Benthic macrofauna found to be abundant, with populations higher in the Amerasia Basin
than in the Eurasian Basin
• Furthest north polar bear on record captured and tagged (84°15′N)
• Demonstrated the presence of polar bears and ringed seals across the Arctic Basin
• Sources of ice-rafted detritus in seafloor cores traced, suggesting that ocean–ice circulation
in the western Canada Basin was toward Fram Strait during glacial intervals, contrary to the
present Beaufort Gyre
• Cloud optical properties linked to marine biogenic sulfur emissions
• Near-surface fresh water found to be derived from river runoff except in the Nansen Basin
where it comes from melting ice
• Arctic Ocean determined to be a source to the atmosphere and Atlantic Ocean of some
organic contaminants, rather than a sink
• Predominant sources of radionuclide contaminants in the ocean found to be from atmospheric weapons testing and European reprocessing plants
THE 1994 ARCTIC OCEAN SECTION
The First Major Scientific Crossing of the Arctic Ocean
Sponsored by
United States
National Science Foundation
Office of Naval Research
U.S. Geological Survey
U.S. Coast Guard
Defense Nuclear Agency
Canada
Department of Fisheries and Oceans
Department of Indian and Northern Affairs
Department of the Environment
Canadian Coast Guard
AOS-94 Chief Scientist: Knut Aagaard
U.S. Chief Scientist: Arthur Grantz
Canadian Chief Scientist: Eddy Carmack
Commanding Officer, CCGS Louis S. St-Laurent: Captain Philip O. Grandy
Commanding Officer, USCGC Polar Sea: Captain Lawson W. Brigham
Published by
U.S. Army Cold Regions Research and Engineering Laboratory
72 Lyme Road
Hanover, NH 03755
Special Report 96-23
Edited by Walter Tucker and David Cate
Compiled by Vicki Keating
1996
1994 Arctic Ocean Section
Contents
— Contents —
U.S. Preface ...................................................................................................................
Canadian Preface ...........................................................................................................
iv
v
INTRODUCTION
Introduction ..................................................................................................................
Chronology....................................................................................................................
The Ships.......................................................................................................................
1
3
8
SCIENCE REPORTS
Introduction ..................................................................................................................
12
Ocean Circulation and Geochemistry
A CTD/Hydrographic Section across the Arctic Ocean ..................................................
Total Carbonate and Total Alkalinity: Tracers of Shelf Waters in the
Arctic Ocean .............................................................................................................
Transient Tracers: Chlorofluorocarbons and Carbon Tetrachloride .................................
Distribution of Iron and Aluminum in the Surface Waters of the Arctic Ocean .............
Thorium Isotopes as Tracers of Scavenging and Particle Dynamics in the Arctic Ocean .
What Can Be Learned from Barium Distributions in the Arctic Ocean? ........................
Biology and the Carbon Cycle
Cycling of Organic Carbon in the Central Arctic Ocean ................................................
Mesozooplankton Community Structure in the Arctic Ocean in Summer......................
Roles of Heterotrophic Bacteria and Protists in the Arctic Ocean Carbon Cycle.............
Contribution of Planktonic and Ice Algae to Dimethylsulfide Production across the Arctic
Ocean in Summer .....................................................................................................
Transfer of Shelf-Derived Carbon to the Interior of the Arctic Ocean ............................
Dimethyl Sulfide in the High Arctic ..............................................................................
The Role of Biomass, Bioturbation and Remineralization in Determining the Fate of
Carbon in the Arctic Ocean .......................................................................................
Oxygen Consumption, Denitrification and Carbon Oxidation Rates in Near-Surface
Sediments of the Arctic Ocean...................................................................................
17
20
23
26
29
32
34
37
40
42
45
47
51
53
Ecology of Marine Mammals
Upper Trophic Level Research: Polar Bears and Ringed Seals .........................................
55
Contaminants
Artificial Radionuclides in the Arctic Ocean ..................................................................
Persistent Organic Contaminants ...................................................................................
Air-Water Gas Exchange of Hexachlorocyclohexanes in the Arctic .................................
59
62
64
ii
Volatile Halomethanes ...................................................................................................
C2–C6 Hydrocarbons ....................................................................................................
67
70
Cloud Radiation
Atmospheric Radiation and Climate Program ................................................................
Aerosols .........................................................................................................................
73
78
Sea Ice
Sea Ice Characteristics across the Arctic Ocean ...............................................................
Measurements of Ice Mechanical Properties ...................................................................
81
86
Geology and Paleoceanography
Sources of Ice-Rafted Detritus and Iceberg Tracks in the Arctic Ocean ...........................
Late Quaternary Paleoceanography of the Canada Basin, central Arctic Ocean ..............
Elemental and Isotope Geochemistry of Sediment from the Arctic Ocean ......................
89
92
95
Ship Technology
Real-Time Remote Sensing for Ice Navigation ...............................................................
Ship Technology Program ..............................................................................................
Hull–Ice Interaction Load Measurements on the CCGS Louis S. St-Laurent ..................
97
100
102
COMMUNICATIONS AND DATA MANAGEMENT
Special Communications Solutions ................................................................................
Data Management .........................................................................................................
104
106
APPENDICES
AOS-94 Participants ......................................................................................................
Science Stations .............................................................................................................
108
114
iii
U.S.Preface
1994 Arctic Ocean Section
— U.S. Preface —
“Nothing great was ever achieved without enthusiasm.”
—Ralph Waldo Emerson
Enthusiasm, cooperation and the spirit of scientific exploration are terms that aptly apply to
the 1994 U.S.–Canada Arctic Ocean Section. The scientific motivation for the undertaking was
to substantially increase the observational base necessary for better understanding the role of the
Arctic in global change. The expedition’s objective was to make a series of measurements that
would allow the analysis and modeling of the biological, chemical and physical systems related to
the Arctic and their impact on global change, and the controlling processes in these systems.
Cooperation was necessary to bring the scientific, operational and funding mechanisms together. Over five years of planning culminated on the evening of 24 July 1994 when the CCGS
Louis S. St-Laurent and the USCGC Polar Sea steamed northward from Nome, Alaska, when 70
scientists embarked with their scientific equipment on what was planned to be a 60-day expedition.
The expedition could not have happened without enthusiasm. There was scientific enthusiasm
for addressing an important and timely research topic. Also there was enthusiasm within the Coast
Guards of the two nations for undertaking a maritime expedition in the Arctic Ocean that was to
be the first of its type for North America.
Although there were challenges and disappointments along the way, the expedition was highly
successful scientifically. The data analysis, interpretation and publication will continue for several
years, and the work will form the basis for new and ongoing research in the Arctic. The National
Science Foundation is proud to have contributed to the project and it congratulates the men and
women who worked so hard to make it a success.
R.W. Corell
Assistant Director, Geosciences
National Science Foundation
U.S.A.
iv
— Canadian Preface —
Unfortunately, in these times of economic restraint, it is not very often that federal managers
get the opportunity to support a highly relevant and focused program that is also stimulating and
exciting. The Arctic Ocean Section provided such an opportunity, and the scientific planners
made sure that the documentation and justification were impeccable. Now that the expedition has
returned and the expectations justified, it is easy to be self-congratulatory. However, without the
considerable groundwork that had been accomplished over a period of several years, nothing would
have happened.
The science plan made sure that maximum use would be made of the platform availability by
considering the broadest possible coverage of issues and disciplines. The legitimacy of the scientific
program was ensured through clear identification of the application of the anticipated results.
Even the logistics and the use of the icebreakers were folded into the science, through programs
dealing with such issues as ice strength, navigation forecasts and hull stresses. Forearmed with
these strong arguments for potential benefits and creative science, the fiscal obstacles proved to
have been surmountable. Despite the considerable difficulties faced, almost all of the anticipated
work was accomplished.
The contents of this report speak, more eloquently than I could possibly hope to describe, on
the success of the mission and the considerable analysis still to be undertaken. It remains for me to
dedicate my thanks to the enormous amount of less exciting, but very necessary planning that laid
the foundation for the funding and approval process.
G.L. Holland
Director General
Oceans Science Directorate
Department of Fisheries and Oceans
Canada
v
1994 Arctic Ocean Section
Introduction
— Introduction —
Traditionally both Canada and the United States have relied on aircraft
and drifting ice camps in supporting scientific work in the Arctic Ocean. Early
examples include the so-called Ski Jump project in 1951–1952 and the ice
stations Alpha and Bravo in 1957. These efforts have been particularly successful in advancing process studies, obtaining certain time series measurements and exploring limited areas; they have been less successful in carrying
out synoptic survey work and sophisticated geographically distributed measurements requiring heavy equipment and elaborate laboratory facilities. In
the open ocean the latter are typically done from shipboard, but not until
1987, when the German research icebreaker Polarstern crossed the Nansen
Basin of the Arctic Ocean, did a modern Western research vessel successfully
operate in the Polar Basin.
Russian scientists had also primarily used aircraft and drifting stations, having pioneered these techniques beginning with Papanin’s North Pole I station
in 1937. While the large and powerful Russian polar icebreaker fleet, one of
which first reached the North Pole in 1977, routinely operates within the
Polar Basin, the vessels are generally not used as scientific platforms. Meanwhile, the voyage of the Polarstern in 1987 was followed in 1991 by a remarkable joint Swedish–German undertaking using the icebreakers Oden and Polarstern to cross both the Nansen and Amundsen Basins, reaching the North Pole
and returning to the Atlantic via northeast Greeenland. A U.S. icebreaker, the
Polar Star, started out with the two European vessels but had to turn back near
85°N because of mechanical difficulties.
Inspired by the planned Swedish–German undertaking, but also deeply
concerned that North American scientists would be unable to participate in
ship-supported work in the Arctic Ocean, Ed Carmack and I met with Canadian and U.S. Coast Guard representatives in Ottawa in the fall of 1989 to
inquire about interest in making a scientific crossing of the Arctic Ocean and
about whether the two Coast Guards thought such an undertaking was realistic. The immediate response was positive on both counts, and the initial target
for the crossing was set as the summer of 1993. The next 58 months or so were
filled with a stream of planning activities involving interested scientific parties, the ship operators and funding agencies. Two major changes were made:
• Because of the long planning time required, the expedition was moved
back one year to 1994; and
1994 Arctic Ocean Section
• Because the yard schedule for the Polar Sea required her to be in Seattle
on 1 October, the route was altered to return directly to the Pacific from
the North Pole, rather than via the Atlantic, that is, crossing the Canada
Basin twice, but with an expected net saving of time.
Thanks to the efforts of a great many caring people, the myriad pieces in
this planning activity all came together, and late in the evening of the 24th of
July 1994 the Louis S. St-Laurent and the Polar Sea steamed northward from
Nome to start the Canada–U.S. 1994 Arctic Ocean Section.
From the beginning the scientific goal of the undertaking had been to substantially increase the observational base necessary for understanding the role
of the Arctic in global change. The objective was thus to make those measurements that would best promote the analysis and modeling of the biological,
chemical and physical systems related to the Arctic and global change, and the
controlling processes in these systems:
• Ocean properties pertinent to understanding circulation and ice cover;
• Biological parameters essential for defining the Arctic carbon cycle;
• Geological observations necessary for understanding past climates;
• Concentration and distribution of contaminants that impact the food
chain and the environment;
• Physical properties and variability of the ice cover; and
• Atmospheric and upper ocean chemistry and physics relevant to climate.
In the following chapters, we shall see how all this came out.
Knut Aagaard
Chief Scientist, AOS-94
Applied Physics Laboratory
University of Washington
Seattle, Washington, USA
2
Introduction
— Chronology —
The CCGS Louis S. St-Laurent and the USCGC Polar Sea departed Victoria, British Columbia, together on the evening of the 17th of July 1994. The
majority of the scientific party of 70 persons boarded by helicopter in Nome,
Alaska, on July 24th; several scientists had sailed with the ships from Victoria
to set up equipment and make preliminary measurements. We sailed through
the Bering Strait on July 25th and entered the ice in the northern Chukchi Sea
early in the afternoon of the following day.
During the first few days, the ships worked some distance apart, as the ice
was not severe. However, from the 30th of July onward, ice coverage was typically complete, and the ships moved close together, operating in tandem for
the most efficient icebreaking, taking turns leading. This greatly reduced the
fuel consumption for the trailing icebreaker. The ships icebreaking in tandem
averaged 3–5 knots during the northbound transit. Visibility was generally
poor throughout the time spent in the ice, with fog and overcast the rule. July
31st was the only full clear day. Passive microwave satellite imagery (SSM/I)
received in real time aboard the Polar Sea provided excellent strategic information on ice conditions for planning the northbound route and stations.
Beginning in the central Chukchi Sea, the station line ran northward east
of the Russia–U.S. Convention line, but once past 200 nautical miles from
Wrangell Island, our track turned northwestward across the Chukchi Abyssal
Plain and onto the Arlis Plateau, which we reached on the 3rd of August at
78°N. Heavy multi-year ice limited our eastward penetration down the flank
of the plateau to longitude 174°18′W. We therefore resumed the station line
northward, with the intent of covering the region to the east along 78°N on
the return voyage. Near 80°N we again attempted a section to the northeast,
but difficult ice conditions limited our penetration in that direction to 80°13′N,
172°46′W. We therefore continued working northwestward across the Mendeleyev Ridge and into the Makarov Basin.
On Monday the 8th of August we had an overflight and data transfer by a
Canadian ice reconnaissance flight carrying side-looking radar, which mapped
the ice in a swath 200 km wide and extending 1100 km along our intended
track northward. From this imagery it was clear that difficult ice conditions
lay to the east. Detailed helicopter ice reconnaissance the next few days confirmed this, and on Sunday the 14th, near 85°N, 170°E, we decided to continue onto the Lomonosov Ridge near 150°E before turning east and running
the final northward leg of the outbound voyage along 150–155°W.
3
1994 Arctic Ocean Section
North Pole
22 Aug ‘94
Keflavik
Nome
Victoria
Seattle
Halifax
Boston
Route of the first
surface circumnavigation of North
America and Greenland. The Louis S.
St-Laurent began
and ended its
voyage in Halifax.
The Polar Sea
began and ended
in Seattle.
Panama
Canal
On the 15th of August the helicopter-borne CTD party found a new undersea mountain when the wire stopped paying out and they brought up mud
from 850 m where the chart showed 3700 m. Three miles away on either side
they found no bottom at 1450 m.
The next three days brought a northeast gale, snow and poor visibility, and
progress was slow through the heavy ice. On the 19th we reached our station
on the crest of the Lomonosov Ridge at 88°47′N, 143°E, where we planned
to turn eastward. There we found the water at intermediate depth to be about
4
Introduction
1°C warmer than we had seen at the base of the ridge, suggesting that the large
gap in the ridge shown in the charts does not exist. We had also observed
sediment-laden ice (“dirty ice”) throughout the long northward track, from
the ice edge in the Chukchi Sea to the North Pole, indicating that sediment
incorporated in the ice on the shallow continental shelves is transported hundreds of kilometers across the Arctic.
Meanwhile, on the 17th we had had ice reconnaissance by a long-range
Canadian aircraft, and on the 19th, while the ships remained on station on
the ridge, we flew a 215-nautical-mile helicopter reconnaissance flight over
the intended track. These showed very heavy ice at the location of our intended
crossing point of the Lomonosov Ridge to the east, so we decided to continue
northward on the section we were on and then return along an alternative
route that would recross the ridge farther south. From there we would attempt
to get onto the eastern flank of the Alpha Ridge to do seismic work and additional piston coring before continuing both these and our many other planned
programs on the long voyage back to Alaska.
However, this was not to be, for shortly after starting northward down the
steep ridge flank, early Sunday morning on the 21st of August, and about 50
nautical miles from the Pole, the Polar Sea lost one of its four blades on the
starboard propeller. Divers also sighted some damage to the blades on the centerline and port shafts. These casualties required that the expedition take the
shortest route out of the ice, which was toward Svalbard. Our intended section northward took us in that direction, and since we had already surveyed
that route by helicopter and knew it to be feasible, we decided to continue on our
course. That same afternoon a U.S. Coast Guard C-130 aircraft from Kodiak
dropped spare parts for our satellite receiver. At 0230 Monday morning, Alaska
standard time, we reached our next science station at 90°N, the first North American surface ships to do so, and the first surface ships ever to do it directly over the
long unexplored route from the Pacific side of the Arctic Ocean. Our station at
the Pole took 28 hours, as we fully deployed every sampling program. Not
only could we compare conditions with those found three years earlier by
Swedish and German investigators, but we could add a great many new measurements (for example, the concentration and distribution of a great variety of
contaminants).
The last few hours before we arrived at the Pole, we had seen a large ship on
the horizon. The ship, which proved to be the Russian nuclear icebreaker Yamal,
had stopped in the ice about 20 nautical miles from the Pole to produce a children’s television program. The Yamal planned to sail south along our intended
track the next day, coincident with the shortest route out of the ice and the one
that we needed to take because of the loss of one of Polar Sea’s propeller blades.
At 0800 on the 23rd we got underway toward Yamal ’s position, 20 nautical
miles to the southeast. Before noon an extraordinary rendezvous took place as the
icebreakers of the three largest Arctic nations—Russia, Canada and the United
5
1994 Arctic Ocean Section
The Russian nuclearpowered icebreaker
Yamal, Louis S. StLaurent and Polar
Sea at an unplanned
rendezvous near
the North Pole.
6
States—commenced a historic polar gathering. More than 550 men, women
and children met near the North Pole on the ice. The Yamal ’s officers and crew
hosted a barbecue on the ice, and the three ships were open for tours. This
unprecedented and impromptu rendezvous near the North Pole in many ways
symbolized a new era of international cooperation in the Arctic Ocean.
That evening all three ships sailed southward together toward Svalbard and
made good progress, reaching south of 86°N by Thursday morning the 25th.
At that point the ice conditions had improved, and we parted company with
the Yamal to resume our scientific work, consonant with expeditiously exiting
the Polar Basin. The pattern of southerly progress in somewhat lighter ice
continued, and we occupied several high-quality science stations in the Eurasia Basin. On the 27th we had an airdrop of helicopter parts. The same day we
received word from the U.S. Department of State that we were not permitted
to continue the work southward within 200 nautical miles of Svalbard. We
therefore terminated our in-ice section with a station at 83°51′N, 35°41′E.
On Tuesday the 30th of August we exited the ice northwest of Svalbard, making course for Iceland. On the 31st we stopped the St-Laurent for a contaminant and oceanographic station in the Greenland Sea at 75°N, 6°W. This
proved to provide an excellent end point for the Arctic Ocean Section, since it
showed the prominent role of the Arctic Ocean outflow in changing the convective region of the Greenland Sea in recent years to a warmer and more saline
state.
The Polar Sea disembarked most of its scientific party in Keflavik, Iceland,
on the 3rd of September and then proceeded to Nova Scotia in company with
the St-Laurent, the ships being slowed enroute by a storm with winds exceeding 60 knots. The St-Laurent disembarked its scientific party in Dartmouth
on the 9th of September, bringing to a close a remarkable and productive
Introduction
voyage. We had completed a highly successful scientific voyage literally across
the top of the world, from the Pacific through Bering Strait, across Canada
Basin, to the North Pole and into the Atlantic via Fram Strait.
Knut Aagaard
Chief Scientist, AOS-94
Lawson W. Brigham
Captain, U.S. Coast Guard
Commanding Officer, USCGC Polar Sea
Eddy Carmack
Chief Scientist, CCGS Louis
S. St-Laurent
Philip O. Grandy
Captain, Canadian Coast Guard
Commanding Officer, CCGS Louis S.
St-Laurent
7
1994 Arctic Ocean Section
— The Ships —
The Canadian Coast Guard Ship Louis S. St-Laurent, a 120-m icebreaker
of 15,324-ton displacement based in Dartmouth, Nova Scotia, is the largest
icebreaker in Canada. The ship has three fixed-pitch propellers. Five diesel
engines supply three propulsion motors that can deliver a total of 30,000 hp
to the three shafts. The Louis S. St-Laurent used an average of 15,000 hp on
the northbound transit; occasional boosts of power to 25,000 hp were required
in heavier ice conditions. The ship carried two BO 105-BS4 helicopters for ice
reconnaissance and science support. Her total crew for this mission was 61,
including the helicopter pilots and mechanic; the science party was 35.
The CTD/rosette, equipped with 36 ten-liter bottles, was deployed from
the boat deck, starboard side. The rosette lab, a joined 16- × 20-ft container,
was immediately forward of the deployment point, and the CTD lab, an 8- ×
12-ft container, immediately aft. Ice work, including access to the ice, was
from the foredeck, which was serviced by two cranes. Net hauls, pump deployments and box cores were done from the foredeck, starboard side. One winch
serviced the net hauls and pumps, while two winches (working in tandem on
deep casts) serviced the box core. Sample processing on the foredeck was done
in an 8- × 12-ft container. All other laboratories were interior to the ship.
The U.S. Coast Guard Cutter Polar Sea is a 122-m icebreaker of 13,600ton displacement based in Seattle, Washington, and is one of two Polar Class
ships, the largest icebreakers in the U.S. The ship has three variable-pitch
propellers. Each shaft can be powered by one or two diesels of 3,000 hp each
(18,000 hp total in full diesel-electric mode) or by a turbine that can supply
20,000 hp in a sustained mode (60,000 hp total in an all-turbine configuration). Only the diesel-electric plant was used during the first portion of the
voyage, but 50 nautical miles from the North Pole the loss of the blade on the
starboard propeller necessitated the use of a gas turbine on the centerline shaft,
boosting her total power to 26,000 hp. The ship carried two HH-65A helicopters for ice reconnaissance and science support. Her total crew for this mission
was 142, including the aviation detachment; the science party numbered 35.
The CTD/rosette, equipped with 24 ten-liter bottles, was deployed from
the main deck, port side, as were the plankton nets. The rosette lab was an
enclosed, fixed, 16- × 14-ft shipboard installation located immediately forward of the deployment area. Ice work, including diving, was done from the
starboard side aft, either using a platform swung from the flight deck by crane
or from the main deck using the gangway. All box and piston coring was done
8
Introduction
from the fantail, where a coring track and J-frame supported the piston coring
work. Seven containers housed the science activities not accommodated within
internal spaces: two on the maindeck, portside, for seismic work; two on the
maindeck, starboard side, for biology, including radioisotope work; one on
the 02 deck, starboard side, for ice core processing; and two on the 02 deck, port
side, for radiation measurements and air and upper ocean chemistry. The latter
container was adjoined by a liquid-nitrogen generating plant producing 3540 L/day in support of a number of science programs. In addition, the port
bridge wing housed a portion of the air sampling equipment. The biological
productivity incubators were sited on the 01 deck, starboard side.
For expedition planning and to enhance navigation through the difficult
ice conditions, an underway “ice center” was established aboard the Louis S.
St-Laurent. Ice information was received from several sources, including realtime satellite imagery, fixed-wing aircraft reconnaissance (synthetic aperture
radar and visual information), helicopter reconnaissance, shipborne radar and
visual surveillance from each icebreaker. Extensive use was made of the real-time
satellite images received and processed aboard the Polar Sea. Special sensor microwave imager (SSM/I from the Defense Meteorological Satellite Program) and
advanced very high resolution radiometer (AVHRR from National Oceanic
and Atmospheric Administration satellites) images were received and processed
using a Terascan system. Sea ice concentration maps derived from the SSM/I
data, which proved invaluable for both strategic and tactical navigation, could
normally be produced and made available for interpretation less than one hour
after a satellite pass. All satellite information could be passed to the ice center
aboard the Louis S. St-Laurent using a VHF-FM ship-to-ship data link.
Effective helicopter ice reconnaissance was crucial to tactical navigation
9
1994 Arctic Ocean Section
CCGS Louis S. St-Laurent
USCGC Polar Sea
USCGC
Polar Sea
CCGS
Louis S. St-Laurent
Year built
1978
1969 (modernized 1988–1993)
Length (m)
122
120
Beam (m)
25.5
24.4
Draft (m)
9.7
9.9
Full-load displacement (tons)
13,600
15,324
Power (hp)
Diesel-electric
18,000
30,000
Turbine
60,000
No. of engines
6 diesel-electric
5 diesel-electric
3 gas turbines
No. of propellers
3
3
Crew
144
59
10
Introduction
during the expedition. Global positioning system receivers aboard the helicopters provided precise coordinates of large floes, leads and other features that
were plotted aboard both icebreakers. A Canadian Coast Guard helicopter
with an Atmospheric Environment Service ice observer aboard flew daily ice
reconnaissance flights in sectors 20–30 nautical miles ahead along the proposed
expedition track. This information, coupled with radar and visual observations
from both ships, greatly enhanced tactical navigation during the voyage.
Knut Aagaard
Chief Scientist, AOS-94
Lawson W. Brigham
Captain, U.S. Coast Guard
Commanding Officer, USCGC Polar Sea
Eddy Carmack
Chief Scientist, CCGS Louis S.
St-Laurent
Philip O. Grandy
Captain, Canadian Coast Guard
Commanding Officer, CCGS Louis S.
St-Laurent
11
1994 Arctic Ocean Section
— Science Reports —
Walter Tucker
In 1896 the Norwegian scientist Fridjof Nansen completed his historic
drift across the Arctic Ocean in the ice-strengthened wooden ship Fram. Several years after his epic scientific voyage, reflecting upon the activities and
achievements of Arctic scientists, Nansen predicted that the Arctic Ocean would
become the best known ocean on Earth. Sadly, a century later, it is the most
undersampled and least understood of the world’s oceans. Canadian, U.S. and
Russian scientists have conducted specific investigations from drifting ice camps
and aircraft landings on the ice for many years, but the formidable ice cover of
the Arctic Ocean has prevented traditional comprehensive oceanographic
transects so common in other oceans of the world. Capable icebreaking vessels
equipped for scientific investigations have been available for little more than a
The CTD/
rosette being
lowered from
the Polar Sea .
FPO
Walter Tucker is from the U.S. Army Cold Regions Research and Engineering Laboratory in Hanover, New
Hampshire, U.S.A.
12
Science Reports
decade. Yet the heavy ice conditions of the central Arctic have required that
major expeditions use two ships. The expense of these scientific voyages has
severely limited the number of comprehensive measurements that can be made
to understand natural processes in the Arctic Ocean.
The Arctic Ocean Section was designed to fill in some of the many
knowledge gaps about the Arctic Ocean. While there were several historic
firsts resulting from AOS-94, most were peripheral to the purposes of the
voyage—to increase our understanding of the Arctic Ocean in the context of
global change and to gather baseline data on contaminants in this region.
With global climate change becoming an issue of international concern,
attention has been increasingly focused on the Arctic, where all effects of global
change are predicted to be amplified. It is also clear that the Arctic plays a key
role in the processes that cause climate
change. For instance, the ice cover of the
Arctic Ocean depends on a delicate and
relatively thin mixed layer that effectively
insulates the ice cover from the warmer
water below. Variations in the stratification may alter the heat and moisture
exchanges with the atmosphere, affecting the balance of all Arctic ice masses.
Predicted increases in air temperature will
affect the extent of the ice cover and therfore the amount of the sun’s heat absorbed
Erk Reimnitz and
Terry Tucker measuring the albedo of
the ice surface.
U.S. Coast Guard
diver preparing to
collect ice algae
samples.
13
1994 Arctic Ocean Section
Dave Paton and
Ikaksak Amagoalik
collecting snow
samples for contaminant studies.
or reflected back to the atmosphere. The fresh water exported from the Arctic
Basin in the form of ice and river runoff into the convective gyres of the Greenland, Iceland and Laborador Seas influences the formation of North Atlantic
deep water and heat transport associated with global thermohaline circulation. The ocean programs on AOS-94 were designed to investigate the ice
cover, water mass structure, origins of the water masses, and ocean circulation
on a major transect of the Arctic Ocean.
Global climate change and the expected increases in atmospheric carbon
dioxide will have a major impact on the carbon cycle of the Arctic Ocean.
Evaluating the internal cycling of carbon plus the fluxes from rivers and adjacent seas is important in understanding what the effect will be on biogeochemical cycling and the ability of the Arctic Ocean to sequester carbon dioxide.
The Arctic Ocean and its marginal seas have only recently been recognized as
areas of high biological productivity during the favorable solar radiation seasons. Primary productivity converts atmospheric carbon dioxide to organic
carbon in the ocean, where it may then be recycled by organisms back to the
atmosphere, remain dissolved in the ocean or be deposited on the sea floor as
particulates. The Arctic Ocean is believed to play an important role in the
global carbon cycle, but too little work has been done to quantify that role. A
major goal of AOS-94 entailed examination of primary productivity levels
and the organic and inorganic carbon pools of the central Arctic.
There is also major international concern that the Arctic has been polluted
by a variety of contaminants, including heavy metals, organochlorines and
radionuclides. Contaminants have been dumped directly into the Arctic Ocean.
14
Science Reports
More important, however, is the ocean’s role as a receptor for contaminants
carried northward by major geochemical transport mechanisms involving the
atmosphere, rivers, sediment, sea ice and currents. Little is known about sources,
background levels, transport pathways and residence times of the various contaminants. Obtaining information on the levels of a variety of contaminants
in the atmosphere, ice, ocean and sediments was the focus of the AOS-94
contaminants program.
AOS-94 was truly multidisciplinary. Fifty individual research programs were
pursued, and the expedition indeed sampled across the entire Arctic Ocean.
The word “section” implies measurements of the seafloor, ocean, ice and atmosphere—a slice from the top of the atmosphere to the bottom of the ocean.
The major disciplinary efforts and their major objectives were:
Ocean Circulation and Geochemistry
Hydrographic surveys and geochemical sampling to improve our understanding of Arctic Ocean circulation and water mass structure.
Biology and the Carbon Cycle
Measurement of standing stocks and production rates of the dominant
organisms and their relation to the distribution of particulate and dissolved carbon and nitrogen.
Ecology of Marine Mammals
Studies of the distribution, migration, population dynamics, genetic history and food chains of polar bears and other marine mammals.
Contaminants
Trans-Arctic sampling of atmosphere, snow, ice, water column and sea
Sediment trap
being lowered into
the water to collect
samples for contaminant chemistry
studies.
15
1994 Arctic Ocean Section
Jim Rich in the
biology van on the
Polar Sea.
16
floor to detect the presence of radioactive wastes and organochlorines.
Cloud Radiation
Characterization of the aerosol and optical properties of clouds, and determination of the greenhouse effect of the Arctic Ocean by quantification
of the major greenhouse gases, UV radiation and photosynthetically active
radiation.
Sea Ice
Determination of ice mechanical, physical and chemical properties, sediment transport by ice, ice biota, contaminants, and albedo of the mottled summer ice surface.
Geology and Paleoceanography
Geoscience sampling to allow an interpretation of tectonic history, past
climates and paleoceanography, and active transport processes in the Arctic Ocean.
Ship Technology
Determination of the utility of real-time remote sensing data for enhancement of navigation through ice and measurement of hull loads
and structural response of the hull to ice loads.
Planned seismic surveys were not accomplished, so the tectonic evolution
program was not successful. All other programs, however, were successful in
spite of the loss of the Polar Sea’s propellor blade, which shortened the voyage.
The following brief reports present details and preliminary results of many of
the research projects.
Ocean Circulation and Geochemistry
— Ocean Circulation and Geochemistry —
A CTD/Hydrographic Section across the Arctic Ocean
James Swift
The objectives of our water column work were:
• To study the origin and circulation of the waters of the
Arctic Ocean and nearby seas;
• To determine the surface-to-bottom distributions and
sources of the physical and chemical characteristics;
• To study the location, origin and structure of subsurface
boundary currents; and
• To contribute to studies of the response of the regimes to
environmental forcing.
The water column program provided the trans-Arctic section a
complete program of CTD (conductivity, temperature and
depth) and “small-volume” hydrographic measurements meeting World Ocean Circulation Experiment parameter and quality
recommendations.
The Louis S. St-Laurent is well equipped for high-latitude
CTD/rosette work. On the starboard side of the vessel there is a
small CTD/computer van and a large double-van rosette room.
The rosette was launched through a large A-frame. The Louis S. St-Laurent is also
outfitted with a full suite of laboratories for the analytical equipment.
We collected water column measurements at 35 hydrographic stations along
the AOS-94 route: beginning on the Chukchi shelf, then across the Chukchi
Abyssal Plain and Makarov Basin, then down the Eurasian side of the Lomonosov
Ridge to the North Pole. Water column work was cut short at that point
because the Polar Sea developed mechanical problems. Both ships exited the Arctic together through Fram Strait, occupying an additional four stations en route.
The U.S./Canadian water column measurement team on the Louis S.
St-Laurent carried out full-depth CTD profiling and 36-level rosette sampling. Water samples were collected for chlorofluorocarbons (CFCs), helium,
oxygen, CO2 system components, AMS 14C, tritium, 18O, nutrients, salinity,
trace metals, radionuclides and organic contaminants. CTD and water sampling was carried out at 39 stations and was remarkably trouble free.
We examined sections of potential temperature, salinity and density anomalies referred to 0 and 2000 db from the CTD data for our section from the
The CTD/rosette
being lowered from
the Louis S.
St-Laurent.
James Swift is from the Scripps Institution of Oceanography in La Jolla, California, U.S.A.
17
1994 Arctic Ocean Section
Potential temperature section from the
Chukchi shelf (left)
to the Eurasian
flank of the Lomonosov Ridge (right).
The warm cores
appear at approximately 200–400 db
above each primary
bathymetric feature.
The station numbers
are across the top
of the figure.
Chukchi shelf to the North Pole. We observed multiple warm cores in the
Atlantic layer (depths of about 200–400 m) near 1.0°C along the Chukchi
boundary and warmer than 1.5°C on the Eurasian side of the Lomonosov Ridge.
Earlier data from the Makarov Basin showed no water in this layer warmer
than 0.5°C. In 1993 the Institute of Oceanographic Sciences (Patricia Bay)
group found water warmer than 1°C on the Makarov slope just north of the
Chukchi Sea. The AOS-94 data extend this finding, showing the Atlantic
layer near both the Chukchi and Lomonosov ridge boundary areas to be 0.5°C
warmer than measured before 1993. In some places the insulating fresh, cold
upper layer was somewhat eroded, though far from completely. One of the
important issues facing us now is to place this warming in context. Such subdecadal variability is important to climate models.
We found the central Canadian sector of the Arctic Ocean to be an oceanographically active environment, not a “dead end” isolated from any active
role in the global circulation by the shallow sill through the Bering Strait, the
Lomonosov and other ridges, and its sheer distance from the North Atlantic
Ocean. Instead, the Canadian sector is importing water, modifying it and
exporting it in ways that have important effects and consequences.
For example, biological activity on the Chukchi shelf is so high in summer that
phytoplankton photosynthesis can supersaturate oxygen in the surface waters there
by almost 50% in places, yet the debris left behind by those organisms and their
predators sinks and decays, regenerating nutrients and using up oxygen on the
bottom of the shelf. These shelf-bottom waters can get rather dense, due partly to
brines released from ice formation above, and then flow off the shelf, carrying
regenerated nutrients and, potentially, contaminants into the central basin.
18
Ocean Circulation and Geochemistry
120
160
Pressure (db)
Oxygen Saturation (%)
Winter shelf waters have been
40
80
0
thought to reach rather high densities. Although there are observations
of this, establishing a direct connec40
tion to the deep waters, which seems
essential to models of deep water for80
mation in the Arctic, has been elusive. We found during AOS-94 what
120
is perhaps an important new piece to
this puzzle: At station 22, on the periphery of the Makarov Basin, we saw
160
a bolus of water dense enough to be
centered at 1000 m, with unique
200
characteristics indicating that it could
have come only from the shelf. Relatively high CFC concentrations confirmed
its recent origin. This bolus has entered the Makarov Basin and now slowly
freshens the deep water. This may be the first direct observation of “new”
high-density shelf water actually in the deep basins.
There is a weak, deep horizontal salinity gradient across the Chukchi–
Makarov sector, with higher deep salinities near the pole on the Canadian side
of the Lomonosov Ridge. At station 22 in the southeastern Makarov Basin we
saw deflections in the salinity isopleths due to the bolus of relatively fresh,
cold, young deep water.
Isopycnals generally slope slightly down from pole to shelf across the domain
covered by this section, with more significant deflections associated with each
principal bathymetric feature, and circulation associated with the bolus of
young deep water found at station 22. Sharp isopycnal slopes over the Lomonosov Ridge (stations 30–34) showed geostrophic adjustment to relatively strong
upper-layer flow along the ridge crest. The most intense deep deflections in
sigma-2 were found on the Eurasian flank of the Lomonosov Ridge and, to a
lesser extent, on the southeast flank of the Makarov Basin.
On their own the AOS-94 CTD/hydrographic/tracer/contaminant data are
a unique, well-placed and important data set, providing the first referencequality section across the Chukchi Abyssal Plain and Makarov Basin and a
careful, synoptic section of closely spaced stations across the Eurasian flank of
the Lomonosov Ridge near the North Pole. The AOS-94 section also joins to
the Oden 1991 section in the Makarov Basin near the Lomonosov Ridge, and
these in turn can be joined to the Polarstern 1987 Nansen Basin section to
form a nearly complete, shelf-to-shelf trans-Arctic section of high-quality surface-to-bottom multi-tracer stations.
Saturation of oxygen vs. pressure for
the AOS-94 stations
over the Chukchi
shelf (Stations 1–6).
19
1994 Arctic Ocean Section
Total Carbonate and Total Alkalinity:
Tracers of Shelf Waters in the Arctic Ocean
E. Peter Jones
Modern oceanographic measurements include a suite of many tracers, each
of which often has a significance in determining the origin of a particular
water mass and tracing its circulation. In the Arctic Ocean, total carbonate and
total alkalinity have been shown to be effective tracers of waters that have
flowed into central regions from the continental shelves. In addition, these
measurements are an integral part of an assessment of carbon fluxes into and
within the Arctic Ocean.
Total alkalinity and total carbonate in seawater are closely related to salinity, with small deviations from a linear relationship resulting primarily from
the dissolution or precipitation of calcium carbonate. In near-surface water,
carbon from biological decay can also be a significant contributor to changes
in total carbonate. Biological productivity can be assessed with the aid of total
alkalinity and nutrient measurements, and the total carbonate and total alkalinity data will contribute to an assessment of the carbon budget of the Arctic
Ocean.
Total alkalinity and total carbonate analyses are best carried out on “fresh”
samples: the analyses were done onboard ship within about 20 hours after
they were collected, using standard techniques (potentiometric titration and
coulometry). Samples were collected at almost all oceanographic stations at
almost all sampling depths, typically 36 from the surface to the bottom, using
the rosette sampler. The time between stations did not allow water from every
sampling depth to be analyzed, though more than 90% of them were. The
quality of the data is high, reflected in replicate analyses with an average difference of just over 1 part per thousand for total alkalinity and 0.9 parts per
thousand for total carbonate.
Higher total alkalinity values observed in the near-surface water at many
stations during AOS-94 are attributed to dissolved calcium carbonate brought
into the Arctic Ocean by runoff. This signal helps to determine the sources of
fresh water by separating river runoff from sea ice meltwater, and it helps in
tracing the circulation pattern of river runoff. Near-surface “excess” alkalinity,
indicating the presence of river runoff, was found at all stations in the Canada
E. Peter Jones is from the Bedford Institute of Oceanography in Dartmouth, Nova Scotia, Canada.
20
Pressure (dbar)
Ocean Circulation and Geochemistry
0
0
50
50
100
100
150
150
200
200
250
250
Station 35
Station 10
300
2300
2400
2500
2600
300
2300
Normalized Total Alkalinity (µM/L)
2400
2500
2600
Normalized Total Alkalinity (µM/L)
Pressure (dbar)
Upper profiles of total alkalinity at Stations 10 and 35 (the North Pole).
0
0
50
50
100
100
150
150
200
200
250
250
Station 35
Station 10
300
2100
2200
2300
Normalized Total Carbonate (µM /L)
2400
300
2100
2200
2300
2400
Normalized Total Carbonate (µM/L)
Upper profiles of total carbonate at Stations 10 and 35 (the North Pole). The maximum values in total carbonate at
Station 10 correspond to maximum values in the nutrient profile and minimum values in the oxygen profile.
21
1994 Arctic Ocean Section
Basin and in the Amundsen Basin. In the Nansen Basin the “excess” total alkalinity was much reduced or not present, indicating that most of the nearsurface fresh water in these regions of the AOS-94 path comes from melting
sea ice.
High values of total carbonate were also observed near the surface. These
correspond to the total alkalinity maximum and are consistent with dissolved
calcium carbonate being brought into the Arctic Ocean by river runoff. There
are also high total carbonate values in the halocline (depth about 100 m) of
the Canada Basin that correspond closely with the nutrient maximum, consistent with the “excess” total carbonate being regenerated along with nutrients
during the decay of biogenic matter. These high values were not present after
Station 14, where the nutrient maximum also disappeared. The total carbonate in the near-surface water and in the halocline can be used to assess the
amounts of carbon entering the Arctic Ocean from the Siberian tundra (river
runoff ) and the amount entering as a result of carbon fixation on the continental shelves.
Profiles of both total alkalinity and total carbonate show small variations in
deeper water that are greater than the precision of these measurements. These
structures may be interpretable in terms of the water masses present and
processes such as the sequestering of anthropogenic carbon dioxide, but any
definitive interpretation will have to await more detailed data analysis, not to
mention inspired thought.
22
Ocean Circulation and Geochemistry
Transient Tracers: Chlorofluorocarbons and Carbon Tetrachloride
E. Peter Jones and Fiona A. McLaughlin
The cloud of international concern over the growing anthropogenic releases of
refrigerants, aerosols and solvents and their impact on climate and the ozone
layer, ironically, has had a silver lining for oceanographers. The measurement
of chlorofluorocarbons (CFCs) and carbon tetrachloride (CCl4) in seawater,
from the surface to the bottom, provides a tool for tracing water masses since
they were last at the sea surface with a time clock that spans most of this
century. Such data give important information about the various layers within
the ocean, for example: Are they rapidly flushed or isolated? Are the waters
transported from other oceans or nearby shelves? These are important questions in Arctic Ocean research, as they relate directly to the transport of contaminants—such as organochlorines and radionuclides—to the Arctic food chain.
Measuring CCl4 may also contribute to understanding the ocean’s ability
to absorb carbon dioxide, a critical question for those attempting to predict
global warming. CCl4 can be used as a surrogate for estimating levels of atmospheric carbon dioxide, as both compounds have been increasing in the atmosphere in a similar fashion since the turn of the century. The depth at which
CCl4 is found in the ocean thus signals the depth at which anthropogenic
carbon dioxide, produced in the twentieth century, is found.
AOS-94 provided an opportunity to measure a suite of CFCs (CFC-12,
CFC-11 and CFC-113) and CCl4 on a transect crossing the Arctic Ocean.
Samples were collected at almost all oceanographic stations at almost all sampling depths, typically 36 from the surface to the bottom, using the rosette
sampler. The samples were analyzed using a standard purge-and-trap gas chromatograph.
Previous cruises sampled different regions in different years: the Nansen
Basin in 1987, the Nansen and Amundsen Basins and the North Pole in 1991,
and the southwestern Canada Basin in 1993. The latter cruise yielded information suggesting that the structure and circulation of water masses in the
Arctic Ocean may be undergoing a major change. AOS-94 CFC data will
allow us to determine the rate, magnitude and extent of these changes.
Although results are preliminary, certain key features are evident. CFC and
E. Peter Jones is from the Bedford Institute of Oceanography in Dartmouth, Nova Scotia, Canada. Fiona McLaughlin is from the Institute of Ocean Sciences in Sidney, British Columbia, Canada.
23
1994 Arctic Ocean Section
0
0
Pressure (dbar)
1000
Station 19
2000
2000
3000
3000
CFC-113
CFC-11
4000
5
10
Concentration (pM/L)
CFC-113
CFC-11
4000
CCl 4
0
Station 29
1000
CCl 4
15
0
5
10
15
Concentration (pM /L)
Profiles of CFC-11, CFC-113 and CCl4 at Station 19 above the Mendeleyev Ridge and Station 29 in the central
Makarov Basin.
0
Pressure (dbar)
1000
2000
3000
CFC-113
CFC-11
CCl 4
4000
0
5
10
Concentration (pM /L)
15
Profiles of CFC-11, CFC-113 and CCl4 at Station 35 in
the Amundsen Basin.
24
Frank Zemlyak and Fiona McLaughlin examining strip chart data in the chemistry lab on the
Louis S. St-Laurent.
Ocean Circulation and Geochemistry
CCl4 profiles obtained at Station 19 above the Mendeleyev Ridge, where boundary currents are believed strong, and at Station 29 in the central Makarov
Basin, where flows are believed to be weak, show important differences in
both the concentrations and the penetration depths of all the compounds.
This suggests that transport mechanisms are stronger around the basin’s exterior than at its interior and that bathymetry plays a major role in the circulation of the Arctic Ocean.
Furthermore, Station 35, east of the Lomonosov Ridge in the central
Amundsen Basin, shows higher values of CFCs and CCl4 in intermediate water layers compared to the central Makarov Basin. This suggests a closer connection with laterally transported incoming source waters. In the deep waters
of the Makarov Basin, greater than 2000 m, concentrations of CFCs and CCl4
are below detection limits, indicating that these waters have a residence time
longer than a century. In the Amundsen Basin the penetration is deeper, with
CCl4 values above the detection limit to beyond 3000 m, signaling that these
waters are less isolated than those in the Makarov Basin. A mesoscale feature is
apparent from temperature and salinity measurements and is confirmed by
CFC concentrations at Station 22 between 900 and 1400 m, about 20% higher
than nearby stations. This eddy-like structure is evidence of a mechanism
whereby waters from the Siberian Shelf are transported into the interior of the
Makarov Basin.
25
1994 Arctic Ocean Section
Distribution of Iron and Aluminum
in the Surface Waters of the Arctic Ocean
Chris Measures
Extremely low concentrations of dissolved iron in the surface waters of
parts of the remote ocean such as the sub-Arctic Pacific are believed to play a
crucial role in limiting the biological productivity of these regions, despite an
abundance of the major nutrients in the surface waters. Phytoplankton require
iron for various biochemical processes, including the conversion of sunlight
energy and the reduction of the nutrient nitrate.
The levels at which iron becomes limiting to phytoplankton growth, and
the effects of its sporadic introduction into surface waters on growth rate, species dominance and carbon export, are the subject of intense study in various
oceanic regimes.
While iron is delivered to the edges of the ocean in copious quantities
through fluvial run-off, little of this material escapes the intense scavenging
removal of these high-productivity regions to reach the surface waters of the
gyres. In the temperate and tropical oceans, iron is delivered to the surface
ocean by the dissolution of eolian-transported continental dust; the regions in
which iron is found to be limiting are those that receive only low inputs of this
eolian material.
Mineral dust inputs to the Arctic are low, and with its annual cycle of variable ice cover, the supply of iron by this route to the surface waters is likely to
be low and highly sporadic in both time and space. Little or nothing is known
of the distribution of iron in the surface waters of the Arctic Ocean, because it
is difficult to collect uncontaminated samples for an element that is ubiquitous in manufactured materials and because of analytical difficulties associated
with determining iron at extremely low concentrations.
Recent advances have resulted in the development of analytical methodology that can be operated onboard ship and is capable of determining iron at
ambient surface water concentrations. AOS-94 provided an opportunity to
deploy this system to investigate the input of the eolian-transported trace metals
iron and aluminum across the surface waters of the basin. Since sampling
close to the ship raises questions of contamination from the ship’s iron hull,
Chris Measures is from the Department of Oceanography at the University of Hawaii in Honolulu, Hawaii,
U.S.A.
26
Ocean Circulation and Geochemistry
Chukchi
Sea
Nansen
Makarov
Basin
Basin
Amundsen
Mendeleyev
Basin
Ridge
8
25
Al
Fe
Dirty Ice
20
6
15
Al
(nM)
Fe
(nM) 4
10
2
5
0
10
20
30
0
40
Station Number
Concentrations of iron and aluminum in the surface waters vs. Louis S. St-Laurent
station numbers.
surface samples were obtained at stations by hand-dipping bottles from the
edge of ice floes located upwind of the ship.
The results indicate that concentrations of iron in the surface waters across
the basin are relatively high and quite variable, with generally higher values
(3.2 nM) in the western Arctic dropping to relatively low values (0.75 nM) in
the Nansen Basin. Within this general trend, though, are localized regions of
extremely high iron concentrations (>8 nM), particularly in the vicinity of the
Mendeleyev Ridge. These highest values occur in regions where the ice floes
were observed to contain significant quantities of sediment on their surface,
known as “dirty ice.” The suggestion that ice-rafted sediment is the source of
these high iron values in the surface water is further supported by the enrichment of aluminum in the same regions.
The entrainment of sediments into ice floes during freezing at the edge of
the basin and the subsequent advection and partial melting of the ice in the
center of the basin represents a unique pathway for delivering reactive trace
metals such as iron to the center of a basin. The partial melting of ice floes
during the summer apparently is capable of delivering high levels of iron to
the surface stratified waters. This delivery mechanism results in relatively high
concentrations of iron, which may favor the development of the ice algae
community that grows on the underside of the ice floes and is thought to
make a major contribution to the primary productivity of the Arctic Ocean.
Large organisms such as ice algae require higher ambient iron concentrations
27
1994 Arctic Ocean Section
Chris Measures
in the laboratory
on the Louis S.
St-Laurent
28
than smaller organisms to meet their iron needs since their requirement scales
with volume but their ability to transport scales with their surface area.
The ice rafting of sedimentary material from the edges to the center of the
basin and its effect on primary production represent a unique biogeochemical
pathway connecting physical, chemical and biological processes. The susceptibility of this transport route to future perturbations of Arctic climatology is
unknown. However, it seems that any change that resulted in the dimunition
of ice-edge freezing in winter might lead to significant changes in the nature
and magnitude of primary productivity of the central Arctic.
Ocean Circulation and Geochemistry
Thorium Isotopes as Tracers of Scavenging and
Particle Dynamics in the Arctic Ocean
S. Bradley Moran, Katherine M. Ellis,
Richard W. Nelson and John N. Smith
The role of the Arctic Ocean in the global carbon cycle remains a key question in studies of global climate change. The Arctic Ocean and its adjacent
seas are characterized by spatial and temporal extremes in the rate of biological
sequestration of atmospheric CO2, ranging from oligotrophic conditions in
the central Arctic to production rates in the Bering and Chukchi Seas that are
among the highest reported for any ocean. An important objective of Arctic
research is to quantify the fraction of total primary production exported from
Arctic surface waters to the ocean bottom in the form of sinking particulate
organic carbon and associated biogenic debris. In addition, the Arctic has the
largest ratio of shelf to deep waters of any oceanic region, making it a particularly good place to study the importance of shelf–basin interactions on particle dynamics and chemical transport.
As part of AOS-94, field sampling was conducted with the primary goals
of:
• Using 234Th as a tracer to quantify scavenging and the export flux of
organic carbon by particle sinking from the upper waters and the coupling of chemical transport between the shelves and the interior Arctic
Ocean; and
• Using 230Th and 232Th to quantify rates of particle cycling in the intermediate and deep Arctic waters.
Collection of these data within the framework of other AOS-94 field programs will contribute to the international effort to better understand the role
of the Arctic Ocean in the global carbon cycle and climate change. Summarized here are preliminary 234Th results of this research. Samples were also
collected for determination of full-depth vertical profiles of long-lived 230Th
(half-life = 7.5 × 104 years) and 232Th (half-life = 1.4 × 1010 years) at several
locations along the cruise track. These samples are being analyzed using highly
sensitive thermal ionization mass spectrometry.
S. Bradley Moran is from the Graduate School of Oceanography at the University of Rhode Island in Narragansett, Rhode Island, U.S.A. Katherine Ellis, Richard Nelson and John Smith are from the Bedford Institute of
Oceanography in Dartmouth, Nova Scotia, Canada.
29
1994 Arctic Ocean Section
Cruise track of the
CCGS Louis S.
St-Laurent and stations occupied for
vertical sampling of
234 Th. Shown in
parentheses are
234 Th/238U activity
ratios in the surface
mixed layer (0–30 m).
Activity ratios less
than one indicate
preferential removal
of 234Th by particle
scavenging, whereas
ratios equal to one
indicate 234Th/238U
equilibrium and very
low rates of particle
scavenging.
30
During AOS-94 the naturally occurring, short-lived 234Th isotope (half-life
= 24.1 days) was used as a tracer to quantify scavenging and the export of sinking biogenic particulate matter and associated elements. In the surface ocean
the disequilibrium between 234Th and its soluble parent 238U varies in response
to short-term changes in particle export on a time scale of approximately 1–
100 days. Because of its short half-life, it was essential to measure 234Th at sea
using a low-energy pure germanium detector.
The 234Th/238U activity ratios in the surface mixed layer (0–30 m) indicates the amount of particle scavenging along the cruise track. The low
234Th/238 U activity ratio of 0.22 at Station 1 is consistent with removal of
234Th from the water column by particle scavenging within the particle-rich
Chukchi Sea. In contrast, surface waters in the interior Arctic generally show
no significant 234Th/238U disequilibrium and hence very low rates of particle
scavenging. An exception is the relatively low 234Th/238U activity ratio of
0.68 at Station 23, which may be due to enhanced biological productivity and
associated biogenic particle scavenging of 234Th at this location.
Vertical profiles of 234Th, 238U and silicate are another way of viewing
particle scavenging. A striking observation is the subsurface deficit in total
234Th evident in the Makarov Basin (Station 26). The low 234 Th activities
may result from scavenging removal of 234Th due to enhanced local biological
Ocean Circulation and Geochemistry
234 Th
0
20
40
Makarov
Basin
(dpm/L)
60 0
20
40
60
North
Pole
Depth (m)
100
200
300
Diss. 234 Th
Part. 234 Th
Diss. 234 Th
Part. 234 Th
Total 234 Th
Total 234 Th
Diss. 238Th
Diss.
238
Si (µM)
400
0
20 40 60
Th
Si (µM)
0 20 40 60
Si (µM)
Depth profiles of 234Th (dpm: disintegrations per minute) and
dissolved silicate in the Makarov Basin and at the North Pole.
238U activities were calculated from salinity ( 238U = 0.069 ×
salinity).
productivity. On the other hand, the 234Th deficit may also reflect a scavenging “history” due to 234Th removal within the particle-rich shelf waters and
advection into the Arctic interior. In contrast, results from the North Pole
(Station 35) indicate no significant 234Th/238U disequilibrium and hence no
appreciable scavenging of 234Th.
These 234Th profiles show for the first time a marked spatial variability in
particle scavenging in the upper Arctic Ocean. Ongoing studies aim to determine the relative importance of 234Th scavenging due to in-situ biological
productivity and advective transport of shelf water containing low 234Th into
the central Arctic.
Finally, the 234Th results are being used to quantify the sinking flux of
biologically produced particulate organic carbon ( POC) from the surface mixed
layer (0–30 m). Preliminary estimates indicate that the export flux of POC
ranges from approximately 400 mg C/m2-day in the Chukchi Sea to 1–10 mg
C/m2-day in the Arctic interior. These particulate carbon fluxes are comparable to the limited number of carbon flux measurements obtained using sediment traps in the Arctic Ocean.
31
1994 Arctic Ocean Section
What Can Be Learned from Barium Distributions
in the Arctic Ocean?
Kelly Kenison Falkner
Barium is one of several naturally occurring inorganic elements that are
being studied as part of a larger project to track river- and shelf-modified
water inputs to the central Arctic. In the open oceans, dissolved barium displays
nutrient-type behavior, being depleted from surface waters in conjunction
with biological processes and enriched at depth by regeneration. River waters
tend to be enriched in dissolved barium with respect to surface seawaters, and
riverine signals are further augmented in estuaries where barium adsorbed on
riverine clays is desorbed as the clays encounter the more abundant cations of
seawater.
AOS-94 samples have been analyzed for dissolved barium content by isotope
dilution-inductively coupled plasma quadrupole mass spectrometry. Several
interesting observations can be made when these results are taken in the context of previously reported barium data for the Arctic (Falkner et al. 1994) and
recent results from 1993–1995 field efforts, including extensive sampling along
the Russian and Siberian estuarine and shelf regions, in the Mackenzie Delta
as well as the 1993 USS Pargo and 1995 Cavalla nuclear submarine missions
(Falkner and Guay, unpublished data). All of these data sets have been calibrated to a common barium standard and have a precision of 3% or better.
Consistent with its higher suspended sediment loads, the Mackenzie River
appears markedly enriched in barium compared to the rivers of the eastern
Arctic sector. Sub-ice surface (< 25 m) barium concentrations in the central
Arctic range from 35 to 70 nM and show a spatial distribution reflecting both
the varying riverine inputs and the integrated surface ice motion. The highest
values are concentrated in the Beaufort Gyre region, which is influenced by
Mackenzie inputs. Intermediate values influenced by the Siberian rivers track
the transpolar drift and are bordered toward the Fram Strait and Barents Shelf
by low values characteristic of North Atlantic surface waters.
As previously observed, halocline waters that display elevated silicon contents and are believed to originate from the Bering–Chukchi regions also show
pronounced barium maxima (up to 140 nM). At stations where halocline
Kelly Kenison Falkner is from the College of Oceanic and Atmospheric Sciences of Oregon State
University, Corvallis, Oregon, U.S.A.
32
Ocean Circulation and Geochemistry
waters do not show a nutrient maximum, barium displays a halocline minimum at levels that correspond to those observed for the eastern Arctic shelf
regions (30–35 nM). Underlying waters of Atlantic origin contain distinctly
higher barium contents of 45–50 nM. These data demonstrate that barium
has considerable promise for complementing other tracers of surface currents
and halocline water formation. Full interpretation of these and other features
in the barium data await complete analyses of the 1995 samples.
Frank Zemlyak in the
Louis S. St-Laurent
chemistry lab.
REFERENCE
Falkner, K.K., R.W. MacDonald, E.C. Carmack and T. Weingartner (1994)
The potential of barium as a tracer of Arctic water masses. In The Polar Oceans
and Their Role in Shaping the Global Environment: The Nansen Centennial
Volume, American Geophysical Union, Geophysical Monograph 85, p. 63–
76 (O.M. Johannessen, R.D. Muench and J.E. Overland, Ed.), Washington,
D.C.
33
1994 Arctic Ocean Section
— Biology and the Carbon Cycle —
Cycling of Organic Carbon in the Central Arctic Ocean
Patricia A. Wheeler
The central Arctic Ocean has been characterized as a region of very low
biological production due to the year-round presence of ice and a short photosynthetic season. Past studies have postulated that the high concentrations of
dissolved organic carbon in surface waters result from the slow growth and
metabolism of bacteria at low temperatures. To determine if biological processes play a significant role in the Arctic carbon cycle, the investigators of the
biology program measured nutrients, particulate and dissolved organic carbon,
standing stocks of algae, micro- and mesozooplankton, and rates of primary production and bacterial production. Standing stocks and production rates are
described in reports by Gosselin et al., Sherr et al., and Thibault. In this summary, I describe major patterns in the distribution of nutrients and organic
carbon along the transect. Then, using biomass and rate measurements made
by other investigators, I estimate the turnover time for the pool of dissolved
organic carbon. The results clearly indicate that significant in-situ production
and utilization of organic carbon takes place in the central Arctic Ocean and
that biological processes play an important role in the Arctic carbon cycle.
Samples were collected at 16 major stations across the Arctic, starting in
the Chukchi Sea, proceeding to the North Pole and exiting on the Atlantic
side. Water samples were collected with a CTD/rosette, after moving ice away
from the ship when necessary. Water samples from 12–24 depths in the upper
300 m were analyzed for nutrient concentrations, particulate carbon and nitrogen, and dissolved organic carbon and nitrogen. Nutrients were analyzed
onboard, while the other samples were stored for later analysis in our shorebased laboratory.
In general, the major nutrients (nitrate, phosphate and silicate) were present
in sufficient concentrations in surface water (0–25 m) to support the primary
production of phytoplankton and ice algae. The one exception was low nitrate
concentrations at stations between 76 and 80°N, 173 and 178°W. In this
region, ice algae in particular may have been nitrogen-limited. Phosphate concentrations decreased from 1.0 to 0.6 µM along the transect, while silicate
Patricia Wheeler is from the College of Oceanic and Atmospheric Sciences at Oregon State University in Corvallis, Oregon, U.S.A.
34
Biology and the Carbon Cycle
concentrations decreased from 10 to
5.0 µM. These decreases may reflect
the relative strength of influence of
Pacific and Atlantic water masses, or
they may reflect biological utilization
of nutrients in water moving in the
Transpolar Drift. Nitrate, however,
showed the opposite pattern. Nitrate
concentrations increased from 1.0 to
4.0 µM along the transect. Nitrate
concentrations varied more with
depth from 0 to 300 m than did
phosphate and silicate concentrations. The wider range in concentrations combined with differences in
diffusion and other mixing processes may account for the differences in patterns of changes in nutrients along the transect.
Particulate organic carbon (POC) ranged from 3.5 to 8.0 g/m2 and generally decreased along the transect. Particulate organic nitrogen (PON) ranged
from 0.4 to 1.3 g/m2 and also generally decreased along the transect. The C/N
ratio of particulate organic material ranged from 8 to 14 and nearly doubled
along the transect. These levels of POC and PON are relatively high; this
material is composed of approximately 40% living material—10% phytoplankton and 30% heterotrophs (bacteria and protists). Zooplankton standing stocks
ranged from 0.2 to 2 gC/m2, making a significant additional contribution to
the total organic carbon and accounting for about 40% of the total particulate
organic carbon in the central Arctic.
The largest pool of organic carbon was dissolved organic carbon (DOC),
which ranged from 60 to 120 µM. DOC and zooplankton standing stocks
both increased in the poleward direction, reaching maximum values around
85 to 87°N. Earlier investigators attributed the high DOC concentrations to
the refractory nature of DOC from riverine inputs and presumably low rates
of bacterial metabolism due to low temperatures in the central Arctic. Gosselin et al. measured significant rates of DOC excretion by phytoplankton and
ice algae; these results, along with the similar spatial patterns of the distribution for zooplankton and DOC, strongly suggest the importance of biological
production of DOC.
Bacterial production ranged from 17 to 53 mg C/m2-day, comparable to
rates measured in Antarctic waters. Since bacteria are the main consumers of
dissolved organic carbon, bacterial production can be used to estimate the
mean turnover time of DOC. Bacterial carbon utilization divided by concentrations of DOC indicated that the average turnover time for the total DOC
pool is less than one year in the central Arctic. Since the mean residence time
Pat Wheeler in the
wet lab aboard the
Polar Sea.
35
1994 Arctic Ocean Section
Mesozooplankton C (gC/m2 )
DOC Excretion (%)
80
a
60
40
a. Percentage of the phytoplankton production released as extracellular carbon, measured by Michel Gosselin.
20
0
2.0
b
1.6
b. Zooplankton standing stocks for 0–100
m. Zooplankton were collected in vertical
net tows (200 mm mesh, 0.75 m opening),
dried onboard ship, weighed and then analyzed for carbon with a CHN analyzer. The
curve is a second-order regression with r 2 =
0.834.
1.2
0.8
0.4
0
140
c
DOC (µM )
120
c. Dissolved organic carbon in the surface
water. Samples were collected in duplicate
and stored frozen with no preservative. The
curve is a second-order regression with r 2 =
0.634.
100
80
60
70
80
90
80
Latitude (°N)
DOC and standing stocks vs. latitude.
of surface water in the central Arctic is about 10 years, some portion of the
DOC is being recycled many times.
Previous studies of the Arctic Ocean carbon cycle assumed that, since production appeared to be low in the central basins, most organic carbon was either
derived from river inputs or imported from the extensive shelf regions. Our
new measurements of primary production, bacterial production and zooplankton standing stocks suggest a more dynamic carbon cycle in the surface waters
of the central Arctic. Higher estimates of primary production result from the
activity of ice algae, which were not sampled in previous studies. Direct measurements of DOC excretion by both ice algae and phytoplankton indicate that
at least a portion of the high DOC found in the central Arctic is produced in
situ. Measurements of rates of bacterial production indicate a significant turnover of DOC in the central Arctic. High standing stocks of mesozooplankton
are further evidence for significant cycling of organic carbon in the upper 100
m of the central Arctic. Primary production by the ice algae and the production of DOC in the central Arctic both appear to be key processes in the Arctic
carbon cycle. Our results indicate that the central Arctic is not a biological
desert but rather supports an active biological community that contributes to
the cycling of organic carbon through dissolved and particulate pools.
36
Biology and the Carbon Cycle
Mesozooplankton Community Structure
in the Arctic Ocean in Summer
Delphine Thibault
Ocean organisms range in size from tiny bacteria (0.1–1 µm) to whales
(over 30 m). Mesozooplankton (200–2000 µm) represent a link between
smaller organisms (<200 µm), such as phytoplankton and microzooplankton (on which they graze) and larger grazers (>200 µm), such as macrozooplankton and fish (which feed on them). By knowing their biomass,
composition and metabolism, we can estimate the role of mesozooplankton in the pelagic food web and the carbon cycle.
During AOS-94, as part of the biological study, the biomass, the specific
composition and the chemical composition of mesozooplankton were estimated in the upper 500 m of the Arctic Basin. Where possible, three layers
were sampled at each station (0–100, 100–200 and 200–500 m). Also, the
content of the gut pigments, as an
indicator of grazing, was directly
measured on the main species and
stages in the upper layer.
The mesozooplankton biomass
in the first 100 m increased quadratically with latitude (r 2 = 0.82),
showing a maximum around 87°N.
A high mesozooplankton biomass
(19–42 mg dry weight/m3) was observed in the upper two layers (0–
200 m), while in the deepest layer
(200–500 m) the biomass was much
lower, ranging from 4 to 16 mg DW/m3. The integrated mesozooplankton
standing stock varied between 0.4 and 10 g DW/m2 and appear to be significantly higher than previously reported for the Arctic Ocean (Conover and
Huntley 1991).
The mesozooplankton carbon content was nearly constant over the
whole study area (around 40% of the dry weight), although it appears to
be lower at the ice edge stations. Those variations might be related to modifications in the zooplanktonic population. The C/N (g/g) ratio for the
The plankton net
being lowered for
sampling on the
Polar Sea.
Delphine Thibault is from the Départment d’océanographie of the Universite du Québec à Rimouski, Quebec,
Canada.
37
1994 Arctic Ocean Section
60
50
50
Gut Pigment Contents (ng Chl a eq/ind)
60
Biomass (mg/m3 )
40
30
20
10
0
70
Pacific
40
30
20
10
80
90
Latitude (°N)
80
0
70
Atlantic
Pacific
Mesozooplankton biomass in the upper 100 m along the
transect. The solid line is a second-order regression, and
the dashed lines show the 99% confidence interval, r 2 =
0.8158.
80
90
Latitude (°N)
80
Atlantic
Gut pigment contents of Calanus hyperboreus female in
the upper 100 m along the transect. The solid line is a
second-order regression, and the dashed lines show the
99% confidence interval, r 2 = 0.86.
mesozooplankton population was high (6.5–8.5) compared to lower latitudes (4.5), but it stayed in the range typical at high latitudes (6.3–12.5)
(Bamstedt 1986). The high lipid content (used as reserve) observed in the
zooplankton may explain these high values.
The Arctic mesozooplankton taxonomic composition did not change
along the transect and within the three depths. This population was mainly
represented by copepods (70–90% of the total number) and specifically by
three large species (Calanus hyperboreus, C. glacialis and Metridia longa) and
three small genera (Oithona, Oncea and Paracalanus). However, the first group
of species accounts for more than 80% of the total biomass and includes
mainly late stages (C4, C5 and adult). The two species of Calanus are typical Arctic species. A third species of Calanus is present but less abundant
(C. finmarchicus, Atlantic species). The highest concentration of this species
was found at the last stations in the Nansen Basin, closest to the inflow of
Atlantic water. In total, 21 species of copepod were identified. This low
number is consistent with the diminution in the number of zooplankton
species with latitude (there are approximately 100 species in the Mediterranean Sea). The other taxa were mainly amphipods, ostracods, pteropods,
isopods, chaetognaths, siphonophores, appendicularia, medusa and
euphausiacea.
The ingestion of phytoplankton by the main species of copepod was
estimated by analyzing the gut pigment content. The values are expressed
38
Biology and the Carbon Cycle
in term of chlorophyll a equivalent (Chl a + pheopigments). The gut pigment content ranged from 1 to 60 ng Chl a eq/individual, with maximum
values (> 10 ng Chl a eq/individual) in the Chukchi Sea and the Nansen
Basin. As with the biomass, those values are well described by a secondorder regression. A good relationship appears between the gut pigment
content and the primary production (for Calanus hyperboreus female, r2 =
0.69). But the high zooplankton biomass in the first 100 m cannot be supported by the chlorophyll a concentration (r2 = –0.7552). On the other hand
this uncoupling, confirmed by the low gut pigment content, might be
explained by the omnivorous character of the main copepods; they can
feed on either phytoplankton or microzooplankton.
All these data give us new information on the role of mesozooplankton
in the Arctic food web. In the Arctic Ocean the zooplankton biomass in late
summer was similar to values reported for other oceans (Reid 1962, Be et
al. 1971). Copepods represent 80% of the whole mesozooplanktonic population of the Arctic Ocean. The contribution of the mesozooplankton in the
carbon cycle is important, accounting for approximately 40% of the total
particulate organic carbon in the upper 100 m of the water column. The
mesozooplankton also feed on phytoplankton but probably more on microzooplankton.
REFERENCES
Bamstedt, U. (1986) Chemical composition and energy content. In The Biological Chemistry of Marine Copepods (E.D.S. Corner and S.C.M. O’Hara, Ed.),
Oxford: Clarendon Press, p. 1–58.
Be, A.W .H., M. Forns and O.A. Roels (1971) Plankton abundance in the
North Atlantic ocean. In Fertility of the Sea, p. 17–50.
Conover, R.J. and M. Huntley (1991) Copepods in ice-covered seas—Distribution, adaptations to seasonally limited food, metabolism, growth patterns
and life cycle strategies in polar seas. J. Mar. Syst., 2: 1–41.
Reid, J.L., Jr. (1962) On circulation, phosphate–phosphorus content, and
zooplankton volumes in the upper part of the Pacific ocean. Limnology and
Oceanography, 7: 287–306.
39
1994 Arctic Ocean Section
Roles of Heterotrophic Bacteria and Protists
in the Arctic Ocean Carbon Cycle
Barry F. Sherr, Evelyn B. Sherr and David Kirchman
Our role in the AOS-94 expedition was to determine the distribution and
activity of heterotrophic microbes (bacteria and phagotrophic protists) in the
context of the overall food web of the upper column. Prevailing theory suggests that bacteria and heterotrophic protists have a minor role in the food
webs of polar ecosystems compared to those of temperate and tropical oceanic
regions, because low water temperatures inhibit microbial growth. According
to this concept, the lack of heterotrophic microbial activity results in a greater
fraction of plant production being available for larger consumers in polar food
webs.
We determined:
• Biomass per unit volume and per square meter for bacteria and for three
size classes of protists;
• Bacterial production and growth rate; and
• Rates of bacterivory.
We also investigated the hypothesis that marine bacterioplankton are metabolically suppressed by extremely low water temperature, by investigating standing stocks and turnover of labile sugars and amino acids and the response of
bacterioplankton to the addition of substrates and to temperature.
The preliminary results indicate an active microbial community. Bacterial
abundances were high (0.5–1.5 × 106 cells/mL) in the upper 50 m of the water
column, declining to < 0.2 × 106 cells/mL below 100 m. Both bacterial and
heterotrophic protist biomass was in the range of 0.4–1.0 g C/m3; the total
biomass of heterotrophic microbes often exceeded the phytoplankton biomass.
Measured phytoplankton production was insufficient to support the rates of
bacterial production; extracellular polysaccharides produced by bottom-ice diatoms are a probable additional source of organic substrate for pelagic bacteria.
Bacterial activity had Q10 values of 2–3 over a temperature range of –1°C
to +15°C. The maximum growth rate was observed at a temperature of about
15°C.
Barry Sherr and Evelyn Sherr are with the College of Oceanic and Atmospheric Sciences at Oregon State University in Corvallis, Oregon, U.S.A. David Kirchman is with the Graduate College of Marine Studies, University of
Delaware, Lewes, Delaware, U.S.A.
40
Biology and the Carbon Cycle
The assemblage of heterotrophic protists was dominated by phagotrophic dinoflagellates from 6 to >50 µm
in size. Ciliates were also common in most samples. There
were few choanoflagellates in
the water column under the
ice pack, although choanoflagellates were abundant in
ice-free waters of the Chukchi
and Greenland Seas, as others
have previously found. The
smallest protists observed were 1–2 µm heterokont flagellates, which appeared to
be feeding both on bacteria and on 1-µm eukaryotic phytoplankton, tentatively
identified as Micromonas pusilla, which were present in abundances of 103–104
cells/mL in the upper 50 m. The protist biomass ranged from 0.006 to 0.1 g
C/m3 and often exceeded estimates of phytoplankton biomass determined
from chlorophyll a concentrations. All size classes and taxonomic groups of
heterotrophic protists appeared to be consuming phytoplankton cells.
Based on the data on standing stock abundance and activity of heterotrophic
microbes in the central Arctic Ocean, and on biomass and production of phytoplankton and ice algae, we developed a preliminary budget of carbon fluxes
through the pelagic microbial food web of the central Arctic Ocean. Integrated
over the upper 50 m, stocks of bacterioplankton ranged from 0.27 to 0.70 g
C/m2, and of heterotrophic protists from 0.37 to 0.79 g C/m2. Estimates of
productivity of autotrophs and heterotrophs in the upper 50 m were comparable: 0.02–0.14 g C/m2-day for bacteria, 0.03–0.25 g C/m2-day for phytoplankton plus ice algae, and 0.05–0.15 g C/m2-day for phagotrophic protists.
Assuming a gross growth efficiency of 40%, heterotrophic microbes could
consume on the order of 0.2–0.7 g C/m2-day. As primary production occurring at the time of the cruise could not provide this daily amount of organic
carbon, we infer that the heterotrophic community was also supported by the
organic carbon present in the water as particulate material (3 g C/m2) and as
dissolved organic compounds (60 g C/m2). This detrital organic matter may
have been produced earlier in the growing season by blooms of ice algae in the
central Arctic.
Our results suggest that, contrary to the initial concept of a minor role of
heteorotrophic microbes in polar ecosystems, heterotrophic bacteria and phagotrophic protists are significant consumers of plant production in the food webs
of the central Arctic Ocean.
Deck incubator for
productivity measurements on the
Polar Sea.
41
1994 Arctic Ocean Section
Contribution of Planktonic and Ice Algae to Dimethylsulfide
Production across the Arctic Ocean in Summer
Michel Gosselin, Maurice Levasseur, Nathalie Simard, Sonia Michaud,
Sangeeta Sharma, Peter Brickell and Timothy Bates
Algae produce a sulfur compound that seems not only to be a key link in
the global sulfur cycles but that also influences the formation of clouds and
therefore the Earth’s temperature. Understanding how these algae affect cloud
formation in the remote oceans could be crucial to predicting how the Earth
will respond to global warming. The link between marine microscopic algae
and climate involves dimethylsulfide, or DMS, the gas that gives air its bracing smell. It forms from the enzymatic breakdown of a salt, dimethylsulfoniopropionate (DMSP). Marine algae produce DMSP to keep their osmotic balance
with seawater, without which water would leave the cells of the algae, killing
them. DMSP may also play a role as a cryoprotectant for microalgae living in
very-low-temperature marine environments, such as polar waters and ice. The
processes by which DMSP is released into the sea are not well understood, but
most researchers think it occurs when algae die or are grazed by zooplankton.
In the sea DMSP breaks down to form DMS. A fraction of this DMS, perhaps
Marine biogeochemical cycle of
DMS: production,
transformation and
utilization pathways
that may ultimately
influence the quantity of DMS lost to
the atmosphere.
Michel Gosselin is with the Département d’océanographie of the Universite du Québec à Rimouski, Rimouski,
Quebec, Canada. Maurice Levasseur, Nathalie Simard and Sonia Michaud are with the Institut Maurice-Lamontagne, Ministére des Péches et des Océans, Mont-Joli, Quebec, Canada. Sangeeta Sharma and Peter Brickell are
with Atmospheric Environment Service, Downsview, Ontario, Canada. Timothy Bates is with the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory, Seattle, Washington, U.S.A.
42
Biology and the Carbon Cycle
Bottom ice community
Sub-ice community
Melt pools community
Planktonic community
Biological communities found in sea ice
and in the upper
part of the water
column in a North–
South section of the
Arctic Ocean during
summer.
a tenth, then enters the atmosphere. The rest is either consumed by bacteria or
broken down by sunlight to form dimethylsulfoxide (DMSO).
Algae exploit several habitats in the polar environment. In ice-free polar
seas, microscopic algae are found mainly in the upper part of the water column. They are called the planktonic algae, or phytoplankton. In ice-covered
seas, algae are found mainly:
• At the surface of the ice in melt pools formed by thawing surface ice,
flooding or a combination of flooding and thawing;
• In the bottom 2–5 cm of the ice, where they form a brownish layer; and
• In the seawater immediately under the ice, where they form huge mats
and strands up to 3 m long.
These unicellular algae that grow in and on the ice are called the sea ice algae.
In the Arctic, phytoplankton and ice algae both contribute to DMS production.
The goal of our study was to determine the contribution of planktonic and
sea ice microalgae to the production of DMSP and DMS in the western and
central Arctic Ocean during summer. Sampling was conducted on the
multi-year ice of the Arctic Ocean from 26 July to 26 August 1994, onboard
the USCGC Polar Sea. The transect began in the continental shelf of the Chukchi Sea on the western side of the Arctic and terminated in the deep Nansen
Basin on eastern side of the Arctic. Along the transect the ice thickness varied
from 1 to 5 m, and ice coverage varied from 50 to 100%. Bottles specifically
designed for oceanographic research were used to collect surface water samples, while melt pools were sampled by means of a bucket. An ice corer was
used for collecting the bottom-ice samples. Finally, the sub-ice samples were
collected by U.S. Coast Guard scuba divers, using a 2-L syringe sampler called
a “slurp gun.” In the laboratory, various measurements were performed on the
melted ice and water samples. Chlorophyll a concentrations, an index of algal
biomass, were determined using the fluorometric method. Particulate DMSP ,
dissolved DMSP and free DMS were determined by gas chromatography.
Significant DMS concentrations were measured in all the habitats studied.
In surface water, DMS concentrations were highest on the continental shelf of
the Chukchi Sea and rapidly decreased toward the Pole. Surface DMS concen43
1994 Arctic Ocean Section
DMS Concentration (nM)
10
trations were also relatively high in
a. Surface Water
8
cracks (openings in the multi-year
ice). These cracks, called leads, tend
6
to be narrow (tens to hundreds of
4
meters in width) but may extend for
2
many kilometers. In some situations
0
leads may reach several kilometers in
30
width and are termed polynyas. Of
b. Bottom Ice
the ice habitats, the highest algal bio20
mass and DMS concentrations were
found in the bottom of the ice on the
10
eastern side of the transect. On a volume basis, the maximum DMS con0
centrations were three times higher
5
in the bottom of the ice than in surc. Sub-ice
face water. Significant DMS concen4
trations were also measured in the al3
gal mats loosely attached to the bot2
tom surface of the ice. These mats,
1
composed of the centric diatom
0
Melosira sp., were found mostly in the
2.5
Canada Basin (from 75° to 80°N and
d. Melt Pools
2.0
from 86° to 88°N) and in the Makarov Basin (from 89° to 90°N). We
1.5
also measured detectable levels of
1.0
DMS in melt pools, which covered
0.5
up to 20% of the surface of the ice.
0
These results indicate that physical
70°
80°
90°
80°
North Latitude
and biological processes occurring at
Latitudinal changes of the DMS concentrathe marginal ice zone of the Chuktion in surface water, in the bottom of the ice,
chi Sea favor DMS production. In the
at the water–ice interface and in melt pools
in the Arctic Ocean in the summer of 1994.
ice-covered central Arctic, although
local sources of DMS exist, DMS
sea-to-air fluxes are probably limited by the gas-tight ice cover. At these high
latitudes, DMS produced by ice algae and phytoplankton may only reach the
atmosphere through leads and other openings in the ice cover.
44
Biology and the Carbon Cycle
Transfer of Shelf-Derived Carbon to the
Interior of the Arctic Ocean
Raymond Sambrotto
The upper water column fluxes of carbon in the Arctic Ocean have been
characterized as dominated by the lateral movement of total dissolved inorganic
carbon (ΣCO2) regenerated from productive shelves to deep water regions. At
least some of this movement is associated with the production and sinking of
brine during sea ice formation on the shelves. This suggests a simple carbon
system in which the abundant organic matter produced on the Arctic shelves
provides the source for the elevated ΣCO 2 found in the upper halocline of
most of the stations thus far examined. At the same time, however, the dominance of such a horizontal flux of carbon would make the Arctic dramatically
different from the carbon systems in lower-latitude basins, which are thought
to be dominated by the vertical flux of organic matter.
Determining the amount of carbon that enters the Arctic is important to
efforts to understand the role of the ocean as a whole as a sink for atmospheric
carbon dioxide and other greenhouse gases that have increased in recent years
due to human activities. The major goal of my research during AOS-94, therefore, was to evaluate the carbon flux in the interior of the Arctic Ocean quantitatively, particularly in the Canada Basin, which has been sparsely sampled.
A total of 164 bottle samples were collected from the surface 400 m of 15
stations along the AOS-94 cruise track of the Polar Sea and were analyzed for
ΣCO 2 using a coulometric technique. Most samples were analyzed onboard,
except samples from the last few stations, which were analyzed upon return to
the laboratory.
The ΣCO2 values measured during the Polar Sea cruise were positively
correlated with salinity, and the maximum values were associated with salinities characteristic of the upper halocline (approximately 33.1 psu). Also, ΣCO2
concentrations were correlated with those of silicate, which suggests that both
signals share a common source on the surrounding shelves, which are sites of
prodigious diatom production during the summer months. The organic material
that is the source of the remineralized ΣCO2, therefore, may be in large part
attributable to diatoms, whose frustules provide much of the silicate as they
dissolve.
Raymond Sambrotto is with the Lamont–Doherty Earth Observatory in Palisades, New York, U.S.A.
45
1994 Arctic Ocean Section
0
Depth (m)
100
200
300
2100
2200
2300
2400
2500
ΣCO2 (µM/kg)
Section of ΣCO2 (mM/kg) from the Chukchi shelf on the left to
the interior of the Canada Basin on the right. The data have
been normalized to a salinity of 35 psu.
Profiles of ΣCO2 (mM/kg) from both the AOS-94
cruise and the 1993 U.S. Navy submarine cruise.
The solid lines represent the average profiles for
the stations in the vicinity of the Lomonosov Ridge,
Chukchi borderlands or central Canada Basin (right
to left, respectively).
The ΣCO2 maximum associated with the upper halocline is most obvious
at stations near the shelf break of the Canada Basin. However, by the northern
end of the Canada Basin, in the vicinity of the former T3 ice station, only
silicate retains a clear maximum in the halocline and ΣCO2 exhibits only a
slight increase between 100 and 150 m. Finally, by the Nansen Basin, little
evidence of any subsurface maximum in nutrient concentrations of any kind
remains.
Perhaps the most significant results of my sampling thus far have been in
characterizing the continuity in ΣCO2 between the shelf and interior regions
of the Canada Basin. With the effect of salinity removed, the large gradient
between the shelf and oceanic regions is clear. The section reflects the continuity between shelf and slope as high-ΣCO2 water (greater than 2200 µM/kg)
detaches from the shelf edge and enters the upper halocline at approximately
100 m. This continuity presumably follows an isopycnal surface between the
two regions.
Additional ΣCO2 data are available for the Canada Basin from a U.S. Navy
submarine cruise in 1993. These data suggest that a significant amount of
inorganic carbon has accumulated under the ice in the central Canada Basin,
where the ΣCO2 content of the upper 300 m is at least 30 moles greater than
the surrounding regions. Thus, the Canada Basin may be an important reservoir for oceanic carbon. Analysis is now focused on isolating the rate at which
shelf carbon is supplied to central regions and the ultimate role of the Arctic in
the global carbon budget.
46
Biology and the Carbon Cycle
Dimethyl Sulfide in the High Arctic
Sangeeta Sharma, Fred Hopper, Peter C. Brickell, Michel Gosselin,
Maurice Levasseur, Natalie Simard and Timothy S. Bates
Natural and anthropogenic emissions contribute approximately equally to
the total global sulfur budget. It is estimated that up to 30–50% of these
natural sulfur emissions are released from the oceans. This can be the largest
source of atmospheric sulfur in ocean regions far from anthropogenic sources
of sulfur.
Clouds
Sun
Change in
Cloud Reflectivity
Climate
Effects
Cloud Condensation
Nuclei
MSA
(particulate)
Non-sea-salt Sulphate
(particulate)
Dry or Wet
Acid Deposition
DMS
(gas)
AIR
Ventilation
OCEAN
Dissolved DMS
(gas)
Algae
Atmospheric fate of DMS, its climate effects and biogeochemical sulfur
cycling in the marine environment.
Sangeeta Sharma, Fred Hopper and Peter Brickell are with Atmospheric Environment Service, Downsview,
Ontario, Canada. Michel Gosselin is with the Département d’océanographie of the Universite du Québec à
Rimouski, Rimouski, Quebec, Canada. Maurice Levasseur and Nathalie Simard are with the Institut MauriceLamontagne, Ministére des Péches et des Océans, Mont-Joli, Quebec, Canada. Timothy Bates is with the National
Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory, Seattle, Washington, U.S.A.
47
1994 Arctic Ocean Section
Equipment used on
the Polar Sea to
analyze DMS samples. The system
consists of a gas
chromatograph with
a sulfur chemiluminescence detector.
Distribution of aqueous dimethyl sulfide
concentrations during the AOS-94
expedition.
48
Dimethyl sulfide (DMS) is the dominant
biogenic sulfur species produced in the
oceans. It is produced by phytoplankton and
is released into the atmosphere at a rate that
depends on variables such as the concentration of DMS dissolved in the water phase,
the wind speed and the temperature. Even
small fluxes of gases from ocean waters can
be globally significant when multiplied by
the area covered by the oceans.
DMS is of particular interest because
of its possible role in climate change. Photochemical oxidation of DMS in the
atmosphere produces fine particles known as cloud condensation nuclei (CCN)
upon which water vapor can condense and form cloud droplets. Changes in the
regional abundance or characteristics of CCN can alter the distribution or properties of clouds, altering the radiative balance through a change in cloud albedo. It
has been hypothesized that DMS is a major link in ocean–atmosphere coupling and may provide a feedback mechanism through which changes in the
global climate are amplified.
Biology and the Carbon Cycle
Numerous model studies have suggested that polar regions are very susceptible to changes in climate. The in-situ measurements of DMS in air and
water made from the USCGC Polar Sea during the transect of the Arctic Ocean
basin have significantly increased the data available on DMS source strengths
and distribution in this sensitive region. Together with the concurrent measurements of CCN and other aerosol and chemical properties of the Arctic
atmosphere, they provide a unique opportunity to investigate the possible
link between DMS, CCN and clouds.
We collected water samples for DMS analysis at the science stations either
with Niskin bottles at various depths or from the ship’s uncontaminated seawater pumping system. DMS dissolved in water was separated by purging,
preconcentrating on adsorbent cartridges and then thermally desorbing into a
gas chromatograph with a sulfur chemiluminescence detector. DMS concentrations in surface seawater samples collected between 24 July and 3 September
ranged from less than 0.1 to 9.1 nM/L. The concentration range was similar
to that observed during the 1991 Oden expedition. Maximum concentrations
were observed along the ice edge and minimum concentrations (below the
detection limit of 0.1 nM/L) at the North Pole.
We collected atmospheric DMS samples using a portable sampler, always
Distribution of atmospheric dimethyl sulfide concentrations
during the AOS -94
expedition.
49
1994 Arctic Ocean Section
60
DMS (nM/m 3 )
40
20
0
20
40
Variation of atmospheric dimethyl
sulfide as a function
of ice cover.
50
on the upwind side of the ship, away
from ship stack emissions and other
sources of contamination. The samples,
collected on cartridges, were kept frozen until analysis (usually within 48
hours of collection). DMS was thermally desorbed from the sample cartridges
by placing the cartridges in the injector
of a gas chromatograph. The DMS was
then transferred to the analytical column
for separation and determined quantitatively by a flameless sulfur chemiluminescence detector. Samples collected
60
80
100
from 18 July to 8 September showed
Ice Cover (%)
atmospheric concentrations from less
than 0.25 nM/m3 (the detection limit) to 50.7 nM/m3, with a median value
of 1.95 nM/m3.
The highest DMS concentrations were found near the ice edge at 67–70°N,
in the Bering Strait and Chukchi Sea regions, and the levels decreased as a
function of ice cover as the ship moved into higher latitudes. This pattern
reversed as the ship exited the ice pack into the Greenland Sea, consistent with
results from the Oden expedition. A diurnal variation was observed in open
water areas, with samples collected at night having values up to four times
higher than in the samples collected during the day in the lower latitudes.
There was not much variation in the ambient concentration once the ship
moved well into the ice pack, but most of these samples were below or just
above the detection limit of the analytical system.
To identify source areas of chemical constituents in the air, we calculated
Langrangian back-trajectories and applied them to the data to determine the
path of air parcels reaching the sampling stations. The most frequent source
area was the northwest Pacific Ocean via the Bering Strait and Chukchi Sea.
Many back-trajectories showed that the air was representative of the high Arctic and had been within this region for several days. A third group of trajectories
showed air originating near Greenland and Iceland.
These results are in agreement with earlier findings on the distribution of
dissolved and atmospheric DMS in the eastern Arctic. Not only was the aqueousphase DMS low in the ice-covered central Arctic Ocean, but ocean–atmosphere
exchange is inhibited by the presence of the ice pack. However, the data available from this complete transect of the Arctic Ocean basin clearly demonstrate that the distribution of DMS along the ice margin and in nearby open
ocean areas is asymmetric. In particular, atmospheric DMS concentrations
were up to ten times higher in the Bering Strait and Chukchi Seas than in the
eastern Arctic.
The Role of Biomass, Bioturbation and Remineralization
in Determining the Fate of Carbon in the Arctic Ocean
Lisa M. Clough, William G. Ambrose, Jr., and J. Kirk Cochran
The goal of biological studies during AOS-94 was to understand the role
of the Arctic in the global carbon cycle. In support of this goal, our research
examined the fate of organic matter reaching the seafloor. Little work had
been done on benthic (seafloor) carbon in the Amerasia Basin prior to this
cruise, but based on work from the Eurasia Basin we surmised that a greater
portion of carbon fixed by pelagic (water column) phytoplankton would reach
the bottom in the entire Arctic Ocean than in other oceans. Possible explanations
for a greater pelagic/benthic coupling included low zooplankton abundance and
feeding rates and a temperature-supressed microbial loop. One of the major
strengths of this cruise was that other researchers were addressing pelagic phytoplankton, zooplankton and microbial processes simultaneously throughout the
cruise.
Our main hypothesis was that the relatively abundant and active benthic
community found in the Arctic is the major factor controlling (both directly
and indirectly) the fate of sedimentary carbon in polar regions. We focused on
some of the possible fates of carbon reaching the benthos by examining patterns
of benthic biomass (how many animals there were), particle bioturbation (how
deep the animals were mixing particles in the sediment) and a variety of estimates of benthic food availabilty (how much total carbon, organic carbon,
chlorophyll, phaeopigments and biologically available protein). In addition
we determined a suite of rate measurements, including remineralization (how
much oxygen is being used by the animals) and bioirrigation rates (how quickly
the animals mix water from above the sediment into the sediment). We collected boxcores from 19 stations along the transect from the coastal waters of
Alaska to the deep basins of the Barents Abyssal Plain. Because of pressure
effects, remineralization experiments were only performed on cores collected
from less than 2000 m deep.
Macrofaunal biomass was ten times higher than has been previously reported
for the Arctic Ocean, supporting the observations made by other members of the
biology group. Mixing rates of both particles and water were directly correLisa Clough is with the Department of Biology at East Carolina University in Greenville, North Carolina,
U.S.A. William Ambrose is with the Department of Biology at Bates College in Lewiston, Maine, U.S.A. J. Kirk
Cochran is with the State University of New York at Stony Brook, New York, U.S.A.
51
1994 Arctic Ocean Section
Lisa Clough preparing a mud sample
on the Polar Sea.
52
lated with macrofaunal abundance, as were sediment
remineralization rates. Given that the surface waters
appeared to be capable of consuming all food being
produced during the cruise, this result is surprising.
It argues that the food supporting the benthos must
be reaching the bottom during the early part of the
summer. We will only be able to test this hypothesis
by being in the Arctic during the early summer.
As a subset of our major question we hypothesized that benthic biomass and processes would
decline from a maximum in the Chukchi Sea to a
minimum under the permanent ice pack and then
begin to increase again towards the more productive
marginal ice zone north of Fram Strait. Instead, we
found that macrofaunal biomass and mixing processes were typically higher in the Amerasia Basin
than in the Eurasia Basin. We are developing a relationship between benthic micro- and macrofaunal
biomass and the flux of particles to the bottom of
the ocean for other regions of the Arctic (in collaboration with Jody Deming of the University of Washington). We hope to be able to use our AOS-94 benthic data to calculate
particulate flux along the AOS-94 transect (a measurement that was not possible during the cruise).
Our analyses of sediment characteristics support the patterns discussed
above. As expected, the depth of the water column above the bottom also
appeared to have an effect on the simple Amerasia versus Eurasia pattern described above. Samples collected from both the Mendeleyev and Lomonosov
Ridges contain more chlorophyll, phaeopigments (breakdown products of chlorophyll) and total carbon than samples collected from deeper depths, even if
the deeper stations were collected nearer to the Alaskan Shelf.
When we combine and compare the estimates of water column productivity, particle flux, gradient-driven sedimentary oxygen flux and sedimentary
carbon burial, we will be able to determine both the degree of pelagic/benthic
coupling in the Arctic Ocean and the role that the benthic animals play in
carbon cycling in the present-day Arctic. Interpreting biological modification
of stratigraphic and pore-water profiles will be critical in determining the present
state of carbon preservation, as well as in understanding the history of the
Arctic Ocean (in conjunction with the researchers studying the geology of the
Arctic Ocean Basin).
Biology and the Carbon Cycle
Oxygen Consumption, Denitrification and Carbon Oxidation Rates
in Near-Surface Sediments of the Arctic Ocean
John P. Christensen
As part of the multidisciplinary AOS-94 expedition, boxcores and piston
cores were collected at a variety of sites across the Arctic Basin. From these
cores, several pore-water solutes, including oxygen, nutrients, alkalinity, pH,
soluble iron and manganese, and sulfate, were measured. Sites ranged from
the continental slope off the Chukchi Sea to the abyssal plains and midbasin
ridges. Ten short cores were used for oxygen profiles, and seven longer cores
were used for the other dissolved solutes over the entire depth of the boxcore.
Profiles of pore-water-dissolved solutes help describe the biogeochemical
sequence of reactions occurring within the sediments. A slight lowering of the
oxygen concentrations was found within the upper few centimeters of pore
waters in all cores. In sites on the continental slope off the Chukchi Sea, porewater nitrate profiles show lowered nitrate concentrations at depth in the sediments. This reduction in nitrate concentrations is attributable to anaerobic
denitrification in the deeper strata of these sediments. These sediments also
received considerable inputs of biogenic material, as indicated by the elevated
levels of dissolved silicate in the pore waters. In contrast, most of the sediments throughout the central basins of the Arctic Ocean are oxygenated over
Kevin O’Toole, John
Christensen, and
Walt Olson standing
by for a box core on
the Polar Sea.
John Christensen is with the Bigelow Laboratory for Ocean Science in West Boothbay Harbor, Maine, U.S.A.
53
1994 Arctic Ocean Section
at least the upper 30–40 cm. No evidence is present for lowered redox conditions, which would support dramatic solubilization of iron or manganese.
Silicate concentrations were elevated over bottom water contents by only 20–
30 µM/L. Measurements of titration alkalinity show concentrations within
the sediments to be higher than those in the bottom waters.
The oxygen gradients will be used to calculate the oxygen fluxes into the
sediments. As this flux is driven by the oxidation of organic matter, rates of
carbon oxidation will be calculated. The alkalinity of the pore waters was increased over bottom water concentrations due to either organic matter oxidation or dissolution of solid-phase carbonate. Fluxes of titration alkalinity out
of the sediments can be compared with fluxes of oxygen to evaluate the relative
importance of these two reactions. Thus, the pore-water profiles will allow us
to estimate the rates of carbon oxidation and carbonate dissolution within
these sediments. In conjunction with estimates of burial and productivity, the
results regarding the rates of organic matter oxidation and carbonate dissolution will be useful in constructing a present-day carbon budget for the central
Arctic Basin.
54
Ecology of Marine Mammals
— Ecology of Marine Mammals —
Upper Trophic Level Research: Polar Bears and Ringed Seals
Malcolm Ramsay and Sean Farley
Nearshore Arctic waters are home to more than a dozen species of mammals
from three orders (Cetacea, Carnivora and Pinnipedia). Prior to the AOS-94
transect, our knowledge of these mammals found in Arctic waters off the continental shelf consisted primarily of anecdotal accounts from explorers’ journals and ships’ logs. Logistical constraints have limited opportunities for biologists to work in the offshore pack ice, so there were few hard data, even on
simple presence or absence, for species outside of a narrow band (about 200
km) from shore accessible by shore-based aircraft. The AOS-94 transect offered
the first dedicated opportunity to monitor polar bears and observe other marine mammals in the permanent pack ice environment of the Arctic Ocean.
Although closely related to the terrestrial brown and black bears of North
America and Asia, polar bears have adopted a marine-associated life style and
are intimately associated with the sea ice of the Arctic Basin. Their southern
range approximates, to a very high degree, the maximum extent of that ice in
winter. They roam over the sea ice in search of their prey, primarily ringed
seals, but bearded and ribbon seals as well. As carnivores, polar bears are at the
top of the relatively long Arctic marine food chain and, accordingly, are nowhere abundant. Furthermore, individual bears move over very large areas
each year in search of their prey.
All polar bears studied to date have been found to be members of relatively
discrete, coastal subpopulations. The northern boundaries for those subpopulations on the periphery of the Arctic Ocean are poorly known. Prior to AOS94, marine mammal researchers assumed that the central Arctic Basin was a
biological desert that could not support a significant biomass of upper trophic
level vertebrates. We viewed participation in the AOS-94 as a pilot project to
determine whether it is feasible for vertebrate ecologists to work productively
in heavy pack ice and whether polar bears and other marine mammals could
be located there.
If bears were found, we wanted to determine what their affinities were with
known coastal-associated populations and how the movement patterns of inMalcolm Ramsay is from the Department of Biology at the University of Saskatchewan in Saskatoon, Saskatchewan,
Canada. Sean Farley is from the Department of Zoology at Washington State University in Pullman, Washington, U.S.A.
55
1994 Arctic Ocean Section
Mother and cub
prior to capture.
56
dividual bears compare with those of bears found nearer to the continental
shelves. To meet our goals we planned to capture as many polar bears as possible and to determine, using genetic and morphological methods, their degree
of affinity with animals from known populations.
The increased use this century of environmentally persistent chlorinated
hydrocarbon (CHC) compounds in industrial and agricultural practices has
led to global contamination of the world’s ecosystems. Although human population densities and industrial activity are low in Arctic regions, CHCs
released in more southerly latitudes are advected north through a variety of
physical processes and eventually reach the Arctic Ocean and its fauna. These
compounds are lipid soluble and tend to become sequestered in the energy
storage tissues of exposed organisms. At each successive stage in a food web,
CHCs become more concentrated in the tissues of the animals, a process called
bioaccumulation. Polar bears are at the top of the relatively long Arctic marine
food web, so their contaminant loads are relatively high and reflect an integration of the entire marine environment. Polar bears can be considered an “early
warning” species reflecting global changes in the Arctic. Consequently a second
goal on the voyage was to collect tissue samples from live-caught polar bears
for monitoring the extent of organochlorine contamination in the remotest
parts of the Arctic marine environment.
A watch for marine mammals was conducted from the bridges of both vessels.
The sea ice was scanned in a narrow band no more than a few kilometers wide
along the track of the ships’ path. When helicopters forayed out from the
Ecology of Marine Mammals
ships, the crews watched for signs of marine mammals. During at least 25% of
the observation time, fog and other atmospheric conditions limited visibility
to a few hundred meters from the ships and precluded helicopter flights.
When animals were seen, their species, number and behavior were recorded.
Polar bears were captured using helicopters and standard immobilization techniques. For each animal, sex was determined, uniquely numbered ear tags
attached, and matching tattoos applied to the left and right upper lip for subsequent identification of recaptured individuals. Age was derived by counting
annuli in the cementum of an extracted vestigial premolar tooth.
Animals were weighed using an electronic scale suspended from an aluminum tripod. Blood samples, adipose tissue biopsies from superficial depots,
and milk samples were collected for subsequent contaminant assay and DNA
sampling. Satellite-communicating radio collars were fitted to adult female
bears to allow us to track them after capture.
We saw 12 polar bears and 15 additional sets of tracks on the expedition. Of
the bears sighted, seven were captured. The remaining five were unavailable
for capture because climatic conditions or extensive open water at the time
made capture unsafe for both the bears and us. Those not captured included
three solitary bears and a female with a yearling cub. We captured and sampled two families, one juvenile male and one juvenile female. None of the
bears handled had previously been marked in any of the ongoing national
polar bear studies along the periphery of the Arctic Ocean.
Both adult females were fitted with a radio transmitter that communicated
with the Service Argos satellites. These radios allowed us to obtain informa-
Captured bear
being prepared
for weighing.
57
1994 Arctic Ocean Section
tion on location and activity patterns. Unfortunately both satellite radio transmitters failed within four months of attachment, possibly due to battery failure. Prior to the loss of radio contact, both bears moved off in a northeasterly
direction, staying in regions of 90% ice cover or greater.
Tissue samples from the bears handled were assayed for organochlorines.
The contaminant loads in the adipose tissue samples from the captured bears
have been determined by R.J. Norstrom (Environment Canada, Ottawa). The
sum of all polychlorinated biphenyls (PCBs) in the bears ranged from 1.7 to
6.6 µg/g lipid, that of the pesticide chlordane from 0.8 to 2.7 µg/g lipid, and
that of the pesticide DDT from 0.1 to 0.4 µg/g lipid. These CHC contaminant loads were in the lower range of values determined for polar bears from
most of the circumpolar, near-land populations. For all three measured contaminants, mean contaminant values in the adipose tissue fell within the lower
50% of mean values for the circumpolar populations of polar bears that have
been sampled previously.
As with bears, more ringed seals were seen than we expected—more than
150, usually singly or in groups of fewer than three. The sighting frequency of
seals remained relatively constant once we were past the continental shelf.
Seals were observed on all except eight days of the transect. On five of those
days, heavy fog limited visibility.
Our sampling protocol was not intended to estimate the population size for
polar bears or ringed seals. We found far more bears (12), tracks of bears (15)
and ringed seals (>150) along our line of transect than anticipated. Clearly
there is a food resource (seals) available to polar bears in the Arctic Basin, and
therefore there may be a resident population of bears. The failure of the satellite tracking program did not allow us to monitor the movements of the two
adult females. The results of the DNA assays and stable-isotopic signatures
from the bears are not yet completed. It is hoped they will support or belie the
hypothesis that polar bears inhabiting the Arctic Ocean basin are indigenous.
Estimating the size of any population of marine mammals in the deep Arctic
Basin is a more difficult problem and will require a concerted effort by researchers from many countries.
Michel Gosselin and other biological oceanographers collected data during
AOS-94 suggesting that a significant, if not major, portion of the food web
exploited by polar bears is associated with the epontic algae, gammarid amphipods and Arctic cod of the multi-year ice floes and not with the pelagic
food column. If corroborated, these findings will give considerable insight
into the ecology of marine mammals. The relative importance of ice algae and
amphipods compared with phytoplankton and copepods may influence the
bioaccumulation of CHCs in the higher trophic levels. Certainly the feeding
ecology of seals and polar bears in any region of the Arctic is poorly understood. As vertebrate ecologists, we eagerly anticipate another opportunity to
study the marine mammals in such a remote and fascinating environment.
58
Contaminants
— Contaminants —
Artificial Radionuclides in the Arctic Ocean
Katherine Ellis, Richard Nelson, John N. Smith,
Linas Kilius and Brad Moran
Recent reports of the dumping of radioactive wastes by the former Soviet
Union in the Barents and Kara Seas have caused concerns regarding levels of
radioactive contaminants in the Arctic areas of North America and their impact
on the environment and human health. These concerns have led to the current
investigation of radionuclide levels and transport pathways in the Arctic Ocean
and the ultimate fate of artificial radionuclides such as 137Cs, 90Sr and 239,240Pu
in the Arctic ecosystem. In addition, these isotopes can provide useful information on transit times for water movement in the Arctic Ocean by relating
isotope concentrations and ratios to their source functions.
Sources of artificial radioactivity of the Arctic Ocean include:
• Fallout from atmospheric nuclear weapons tests carried out mainly in the
1950s and 1960s;
• Effluent from European reprocessing plants (including Sellafield in the
U.K. and Cap le Hague in France);
• Releases during the Chernobyl accident in 1986;
• Solid and liquid radioactive waste, including spent reactor cores from
nuclear submarines and ships, dumped in the Barents and Kara Seas by
the former Soviet Union;
• Nuclear wastes transported down Russian rivers; and
• Nuclear wastes discharged into coastal waters associated with the present
Russian nuclear fleet.
Artificial radioactivity is transported into the Arctic Ocean via several pathways. Atlantic water, carrying atmospheric fallout and effluent from Sellafield
and Chernobyl, is transported into the Arctic Ocean via Fram Strait or the
Barents Sea, where it may incorporate releases from Russian radioactive waste.
Pacific water flowing in through Bering Strait carries atmospheric fallout from
the Pacific Ocean. Surface water on the Russian continental shelves, containing Atlantic and Pacific water and river runoff, is mixed and advected into the
Arctic Ocean surface layer. Dense saline plumes, produced during ice freezing
Katherine Ellis, Richard Nelson and John Smith are with the Bedford Institute of Oceanography in Dartmouth,
Nova Scotia, Canada. Linas Kilius is with IsoTrace Laboratory at the University of Toronto in Toronto, Ontario,
Canada. Brad Moran is with the University of Rhode Island in Narragansett, Rhode Island, U.S.A.
59
1994 Arctic Ocean Section
Sources of artificial
radionuclides in the
Arctic Ocean.
60
in shelf regions, are transported down
into the halocline, intermediate and
deep water layers of the Arctic Ocean.
Particle reactive isotopes can also be
transported into the interior of the
Effluent
From
Arctic Ocean through incorporation
Effluent
from Russian
Russian
ProcessingPlants
Plants
Processing
into ice and subsequent release of the
ice-rafted radioactive contaminants
Russian
Nuclear
Russian Nuclear
Test Sites
Test
Sites
into the water column and sediments
by melting or breakup of the ice.
Russian
Radioactive
Russian Radioactive
Until recently, studies of the transDumpsite
Dumpsite
port of artificial radioactivity into the
Arctic Ocean had been limited to
Effluent
the
EffluentFrom
from the
measurements conducted from a few
Sellafield
Sellafield
Processing Plant
Processing
Plant
ice stations, such as LOREX (1979),
AtlanticWater
Water Flow
Flow
Atlantic
FRAM3 (1981), CESAR (1983), AIWEX (1985) and the Canadian Ice
Island (1985–1989). The use of icebreakers during AOS-94 has vastly increased the number of sampling locations in the western Arctic Ocean. Water samples were collected from many of
the major areas of the Arctic Ocean, including the Chukchi Sea and the Canada, Makarov, Amundsen and Nansen Basins. Sediment cores were collected
in areas of sediment accumulation along the cruise track.
The levels of artificial radionuclides in Arctic Ocean water are low and
require concentration from large volumes of water in order to measure the
levels by conventional counting techniques. Samples were collected either by
combining several Niskin bottle samples from the rosette sampler or by using
pumps to pass water through resins and absorbers that remove and concentrate specific isotopes. Cesium isotopes (137Cs and 134Cs) were counted on
KCFC (potassium cobalt ferrocyanide) resin. Strontium, plutonium and americium isotopes (90Sr, 239,240Pu, 238Pu and 241Am) were concentrated from 60
to 100 L by precipitation, and the concentrates were returned to the laboratory for further purification and counting. Sediment cores were subsampled
and analyzed at 1-cm intervals. Sediment analyses are being used to calculate
sediment inventories of artificial radionuclides and to identify areas of net
accumulation.
Preliminary measurements for 137Cs and 129I clearly show the presence of
Sellafield and Chernobyl contaminants in surface and Atlantic-layer water
throughout the Arctic Ocean. The main exception was surface water in the
Chukchi Sea, where Pacific-origin water, containing only atmospheric fallout,
flows in through the Bering Strait. The highest activities (12–15 Bq/m3 for
137Cs and 80–100 × 107 atoms/L for 129I) were found over the Lomonosov
Ridge near the North Pole, consistent with the surface circulation pattern of
Contaminants
0
Water Depth (m)
the Trans Polar Drift, which carries surface
water from Siberia across to Greenland. The
high activities and ratios of isotopes 129I/
1000
137Cs and 134 Cs/137 Cs identify the source
as European reprocessing plants and Cher2000
nobyl fallout and indicate that the late-1970s
peak of Sellafield-labeled water has now
passed over the central Arctic Ocean, approx3000
imately 15 years later. A comparison of the
137Cs profile measured at the North Pole to
LOREX (1979)
4000
profiles measured in 1979 and 1991 illusOden (Sta. 173, 1991)
trates the history of the transport. In 1979
AOS (Sta. 35, 1994)
the water column contained 137Cs mainly
5000
0
4
8
12
16
20
derived from atmospheric fallout, before the
137
Cs (Bq/m3)
Chernobyl accident and before effluent from
European reprocessing plants had reached the Atlantic layer of the central 137Cs profiles measat the North
Arctic Ocean. A large increase in the 137Cs inventory in surface waters by ured
Pole in 1979, in
1991 and 1994 was caused by the arrival of Sellafield and Chernobyl 137Cs. 1991 and during
The 137 Cs levels below 1000 m are not significantly different from those meas- AOS-94.
ured in 1979, indicating the continued maintenance of a pronounced Sellafield signal at this depth since 1979. The results from the sediment analysis
indicate that the shelf slope sediments of the Chukchi Sea contain the highest
inventory of artificial radionuclides, while the central Arctic areas have the
lowest inventories.
Preliminary results provide little evidence of radioactive contamination of
the Arctic Ocean from Russian sources. However, the transport pathways of
potential contaminants can be delineated through studies of tracers from European reprocessing plants. Although the magnitude of the artificial radionuclide
signal measured in the Arctic Ocean may be a factor of ten greater than levels
due to atmospheric nuclear tests, these levels are significantly lower than levels
that would constitute a radiological threat to organisms or humans along the
North American coast.
61
1994 Arctic Ocean Section
Persistent Organic Contaminants
Robie Macdonald and Fiona McLaughlin
Rob MacDonald
collecting Arctic
cod for contaminant studies.
AOS-94 provided a unique opportunity to collect contaminant samples
across a large, unsampled portion of the Arctic Ocean. One strength of this
contaminant study is that the transect crossed all major atmospheric and ice
transport routes, water bodies and three of the four main basins within the
Arctic Ocean. A second strength is that samples were collected in conjunction
with physical and biological data. In contrast, because of limited accessibility,
previous investigations have produced a patchwork of data, collected by different groups using a variety of methods over time, generally focusing on smaller,
specific regions.
Our strategy for sample collection was to examine each of the major environmental compartments; ice, water, particles, plankton, fish and sediments.
Beginning with the water column, we adopted several strategies. Vertical profile
samples were collected for the most water-soluble organochlorine contaminant, hexachlorocyclohexane
(HCH; one form, alpha, is the pesticide Lindane), at
selected stations from the Chukchi to the Greenland
Seas. These samples will provide the basis for producing an HCH budget for the Arctic Ocean and
may allow us to separate the contributions by source
or pathway (southeast Asia versus northern Europe).
Other less-soluble organochlorine contaminants, such
as PCBs, require collection of larger quantities of water
in order to make reliable measurements. To collect
samples for these analyses, we moored submersible
pumps equipped with columns and filters to obtain
the 400 L or more of water required to exceed detection limits. Vertical profile samples for these less-soluble contaminants were collected at two stations; these
data will augment the limited profile data collected
at the Hobson’s Choice Ice Island in 1986 and in
the Beaufort Sea in 1992.
Robie Macdonald and Fiona McLaughlin are with the Institute of Ocean Sciences in Sidney, British Columbia,
Canada.
62
Contaminants
Samples of suspended particulate material
were collected in the top 30 m of the water column at many stations using a system capable of
pumping and filtering large volumes of water
quickly. These samples will help us to determine
the fractionation of contaminants between dissolved and particulate phases, an important aspect
of the process of scavenging and removal of contaminants from the euphotic zone.
Samples of zooplankton were collected using
vertical net hauls in the top 100 m of the water
column. These will be analyzed for organochlorine contaminants, which will determine the level
of biomagnification in the lower part of the food
chain. Cod, a species higher in the food chain,
were collected opportunistically across the transect. By combining the zooplankton and cod data,
we have a unique view of both bioaccumulation
and biomagnification of organochlorines in the
food chain across this section.
Sediment cores were collected at eight stations
spanning the cruise track. Samples from these
cores will be analyzed to provide information on particle-active contaminants,
for example, lead, highly chlorinated organochlorines and PAH (polynuclear
aromatic hydrocarbon). The levels of these contaminants will be examined to
determine both the spatial trends across the transect and the importance of
sediments as sinks for contaminants within the Arctic Ocean.
Although many samples are already under analysis, we do not yet have any
contaminant data for AOS-94. The process of analysis is complex and lengthy,
involving several analytical tools, for example, high-resolution mass spectrometry
and electron-capture gas chromatography. Information from the Larsen-93 cruise,
which collected samples from a region that overlaps the early portion of the AOS94 transect, suggests that we will find regional differences in contaminants
produced both by delivery mechanism (transport within water masses) and by
removal mechanism (biological productivity and the supply of particles). Understanding the relative importance of these mechanisms is crucial to our ability to predict the effects these compounds are likely to have on the Arctic
community and the time required for a response to any environmental change,
including a removal of the source.
Fiona McLaughlin
drawing water samples from the Niskin
bottles for chemistry
analysis on the
Louis S. St-Laurent
63
1994 Arctic Ocean Section
Air-Water Gas Exchange of Hexachlorocyclohexanes in the Arctic
Liisa Jantunen and Terry Bidleman
Our objectives for the AOS-94 cruise were to measure the transfer of chlorine-containing pesticides between the atmosphere and the Arctic Ocean. The
focus was on pesticides that have largely been banned in Canada and the United
States but are still used in other countries. These chemicals are emitted into
the atmosphere through current usage and volatilization of old residues from
soils. Air currents carry them to remote areas worldwide, including the Arctic.
One pesticide of special interest was hexachlorocyclohexane (HCH).
HCH is applied as a technical mixture that contains several isomers, largely
α-HCH (60–70%), β-HCH (5–12%) and γ-HCH (10–15%) (Iwata et al.
1993). The active ingredient, γ-HCH, is also produced in pure form and sold
as the pesticide Lindane. Both insecticides were produced during World War
II and are still in large-scale use today. Canada banned technical HCH in
1971, followed by the United States in 1978. Lindane is still registered for restricted applications in these countries and is the main HCH product used in Europe
(Barrie et al. 1993, Hinckley et al. 1991). Technical HCH was heavily used in
Asian countries throughout the 1980s. Reports from India range from 20,000 to
47,000 tons/year (Iwata et al. 1993, Hinckley et al. 1991). It is estimated that the
cumulative worldwide use since the introduction of HCH products is over 500,000
tons (Voldner and Li 1995). Because of their widespread usage and ease of transport, HCHs are the most abundant pesticides in the Arctic air and surface
waters.
Air was sampled by drawing approximately 700 m3 per day through a filter
followed by a polyurethane foam cartridge. HCHs were extracted from water
by passing 4–20 L through a filter followed by a C8-bonded silica cartridge.
Analysis was done in the home laboratory, using capillary gas chromatography
with electron capture detection and negative ion mass spectrometry.
The accompanying figures show the results of air and water sampling for
α-HCH; they also contain data collected in the Bering and Chukchi Seas in 1993
aboard the Russian R/V Okeah to complete the overall picture. The figures show
the spatial distribution of α-HCH, from the Bering Sea to the Greenland Sea over
the North Pole. Concentrations of α-HCH in water of the Bering and Chukchi
Seas averaged 2.00 ± 0.48 ng/L (Jantunen and Bidleman 1995), increased in
Liisa Jantunen and Terry Bidleman are with the Atmospheric Environment Service, Downsview, Ontario,
Canada.
64
Contaminants
6
a. Water
5
(ng/L)
4
3
(pg/m3 )
i R ti
1
ti
0
140
b. Air
120
HCH E
α-HCH Concentration
2
100
80
60
40
Bering Sea
Latitude (°N)
55 - 45
67 - 61
77 - 67
84 - 80
89 - 85
85 - 89
80 - 84
75 - 79
70 - 74
65 - 69
60 - 64
55 - 59
0
50 - 54
20
Greenland Sea
Surface water and air concentrations of α-HCH measured on BERPAC93 and AOS-94, averaged within
bands of 5° latitude.
1.2
c. Water
1.1
1.0
0.9
α-HCH Enantiomeric Ratio
0.8
0.7
1.2
d. Air
1.1
1.0
0.9
Bering Sea
Latitude (°N)
55 - 45
67 - 61
77 - 67
84 - 80
89 - 85
85 - 89
80 - 84
75 - 79
70 - 74
65 - 69
60 - 64
0.7
55 - 59
0.8
50 - 54
the Arctic Ocean to 4.61 ±0.45 ng/L and decreased
in the Greenland Sea to 1.52 ±0.33 ng/L. The
trend of α-HCH in air was opposite to that found
in the water. The concentrations were highest over
the Bering and Chukchi Seas (123 ±16 pg/m3)
and the Greenland Sea (119 ±16 pg/m3) but decreased dramatically over the Arctic Ocean (57 ±20
pg/m3). The dip over the polar ice cap may be due
to rain scavenging by fog and drizzle and inhibited
revolatilization from surface water by the ice cap.
The water/air fugacity ratio can be calculated
from the α-HCH concentrations in air and water
and the temperature-dependent Henry’s Law constant. The fugacity ratio expresses the saturation
state of surface water relative to the partial pressure
of the α-HCH in air. In the 1980s fugacity ratios
of α-HCH were less than 1.0 in Arctic and subArctic waters, indicating that the surface water was
undersaturated and the net flux was air to sea. Our
measurements in the Bering and Chukchi Seas
(Jantunen and Bidleman 1995) and on the AOS94 cruise show that concentrations of α-HCH in
the air have decreased by three-fold since 1990.
Reducing the partial pressure of α-HCH in air has
raised fugacity ratios to above 1.0. Thus the surface
waters are now oversaturated and volatilizing αHCH.
Release of α-HCH from the ocean can be sensed
by following the proportion of its two enantiomers
in water and air. Enantiomers are mirror-image
molecules that have the same physicochemical
properties but that often differ in their biochemical characteristics. Right- and left-handed amino
acids are familiar examples, and α-HCH is similar. The enantiomeric ratio (ER) of α-HCH is defined as (+)α-HCH /(–)α-HCH. The ER in the
manufactured pesticide is 1.00 (racemic) and is
not changed by abiotic reactions such as hydrolysis and photolysis. However, enzymes can and frequently do react selectively with one enantiomer,
leading to ERs that differ from 1.00 (Buser and
Muller 1995). We have found selective depletion
of either (+) or (–) α-HCH in surface water, pre-
Greenland Sea
Enantiomeric ratios of α-HCH in surface water and
air in the same bands of 5° latitude.
65
1994 Arctic Ocean Section
sumably the result of microbial degradation. These enantiomeric “signatures”
of α-HCH are reflected in the overlying air, providing a direct indication of
sea-to-air transfer.
The accompanying figures show the ERs of α-HCH in water and air with
latitude. In the Bering and Chukchi Seas the ERs are greater than 1.00, indicating a degradation of (–)α-HCH relative to (+)α- HCH. Selective breakdown
of (+)α-HCH in the Arctic Ocean and the Greenland Sea reverses the ERs to
less than 1.00. These enantiomeric profiles are also found in air samples collected over open-water regions, indicating volatilization of α-HCH from surface
water. The α-HCH in air over the ice cap was near racemic. Fugacity ratios at
higher latitudes also show the potential for α-HCH to volatilize (this work and
Falconer et al. 1995), but fluxes are probably inhibited by the ice cover.
Using the ER of α-HCH provides a way of distinguishing α-HCH that has
been microbially processed and recycled to the atmosphere by the oceans from
“fresh” α-HCH that has undergone aerial transport from source regions.
Enantiomers of chiral pesticides, such as α-HCH, chlordanes and heptachlor,
may also prove useful for tracing water masses with different ER signatures
when employed with traditional tracers such as salinity, temperature, nutrients and dissolved oxygen.
REFERENCES
Barrie, L.A., D. Gregor, B. Hargrave, R. Lake, D. Muir, R. Shearer, B. Tracey
and T. Bidleman (1992) Arctic contaminants—Sources, occurrence and pathways. Science of the Total Environment, 122: 1–74.
Buser, H., and M. Muller (1995) Isomer and enantioselective degradation of
hexachlorocyclohexane isomers in sewage sludge under anaerobic conditions.
Environmental Science and Technology, 29: 664–672.
Falconer, R., T. Bidleman and D. Gregor (1995) Air–water gas exchange and
evidence for metabolism of hexachlorocylohexanes in Resolute Bay, NWT.
Science of the Total Environment, 160/161: 65–74.
Hinckley, D., T. Bidleman and C. Rice (1991) Atmospheric organochlorine
pollutants and air–sea exchange of hexachlorocylohexane in the Bering and
Chukchi Seas. Journal of Geophysical Research, 96: 1702–1713.
Iwata, H., S. Tanabe, N. Sakai and R. Tatsukawa (1993) Distribution of persistent organochlorines in the oceanic air and surface seawater and the role of
oceans on their global transport and fate. Environmental Science and Technology, 27: 1080–1098.
Jantunen, L., and T. Bidleman (1995) Reversal of the air–water–gas exchange
direction of hexachlorocyclohexanes in the Bering and Chukchi Seas. Environmental Science and Technology, 29 (4): 1081–1089.
Voldner, E., and Y. Li (1995) Global usage of selected persistent organochlorines. Science of the Total Environment, 160–161, 201–206.
66
Contaminants
Volatile Halomethanes
Robert M. Moore and Charles Geen
Volatile organohalogens have an important influence on atmospheric chemistry. In particular, halogenated methanes provide a source of atmospheric
chlorine and bromine radicals, which can affect ozone concentrations. There
has been shown to be a strong correlation between elevated atmospheric concentrations of brominated substances and sudden tropospheric ozone depletion
events, especially during the Arctic spring. There are also indications that brominated compounds play a significant role in stratospheric ozone destruction.
It is important to distinguish between natural and anthropogenic inputs of
these compounds. In attempting to understand the ozone depletion events in
the Arctic boundary layer, there has been considerable interest in examining
the natural Arctic marine origins of volatile bromine compounds (bromoform
in particular) as potentially significant sources of gaseous halogens to the atmosphere. Our research group has previously found evidence of an ice-algal source
of bromoform and dibromomethane in the Arctic. Evidence also exists in northern waters for a phytoplankton source of volatile iodine compounds, which
can play a role in the biogeochemical cycling of iodine and in atmospheric
chemistry.
Our objective in participating in the AOS-94 cruise was to extend the database of measurements of distributions and concentrations of brominated, chlorinated and iodinated methanes in the Arctic Ocean. This would contribute to
the goal of determining the natural origins of these compounds; in fact, this
expedition was the culmination of a five-year, Arctic-wide study of the sources
of such substances. Measurements were also made of the trace gas concentrations
in seawater that had been allowed to equilibrate with the atmosphere; these
are needed for calculating fluxes of the gases between the ocean and the atmosphere.
Almost 500 seawater samples were analyzed by gas chromatography during the cruise. Vertical profiles from many stations provided further general
oceanographic knowledge of water column distributions of the halomethanes
and generally showed the concentrations of the halocarbon gases of interest to
be higher in the surface waters and to decrease with depth. However, since our
Robert Moore is with the Department of Oceanography at Dalhousie University at Halifax, Nova Scotia,
Canada. Charles Geen is with Bovar-Concord Environmental in Toronto, Ontario, Canada.
67
1994 Arctic Ocean Section
Laboratory on the
Polar Sea equipped
for analysis of atmosphere and ocean
contaminants.
[Photo by Peter
Brickell.]
interests were principally the origins and behavior of naturally produced volatile halocarbons in the upper ocean, the work focused on surface-water
distributions and the results from the equilibration experiments. Initial data
analysis centered on the primary compounds of interest—bromoform (CHBr3),
dibromomethane (CH2Br2) and chloroiodomethane (CH2ClI)—but data are
being processed for other compounds in our suite of analytes, including bromodichloromethane (CHBr Cl2), chlorodibromomethane (CHBr 2Cl ), methyl
iodide (CH3I) and diiodomethane (CH2I2).
The results of the equilibration experiments indicate that the direction of
flux will be from the ocean to the atmosphere, since the water is supersaturated
with respect to the air. The water column is stably stratified, so there is little
downward mixing. Other dissipation processes, such as hydrolysis and substitution reactions, are relatively slow, so ventilation to the atmosphere is likely to
be the main short-term removal mechanism for any of these dissolved gases in
the seawater.
The results of our seawater measurements during AOS-94 indicate that
some of the halomethane concentrations in the upper water column at these
high latitudes beneath the polar ice pack are relatively high, even during late
summer and early fall. For example, bromoform concentrations at most stations
are equal to or greater than any others that we have previously measured from
spring to autumn in the open ocean waters or beneath the ice of several Arctic
regions, including Baffin Bay, Alert, Resolute Bay, the Beaufort Sea, the Bering
Sea and the Chukchi Sea. It would appear that while temporal variations may
be relatively large in open ocean areas and in regions where the ice cover melts for
part of the year, they may not be as great in permanently ice-covered regions.
The unexpected picture emerging from the AOS-94 expedition—that halomethane concentrations remain high beneath the polar ice cap throughout
68
Contaminants
the summer and into the fall—means it is likely that even in winter, when
such substances may not be produced, large amounts would still be present in
surface waters. If in fact there is a fairly constant source of halomethanes beneath the ice pack, any lead, crack, polynya or open water could provide a flux
of these gases to the atmosphere at any time. In this case the question of the
possible origins of the Arctic springtime atmospheric pulse of bromine then
becomes one of physics and ice dynamics. That is, how often, and for how
long, are open-water areas present in the Arctic during the dark winter and
early spring?
Finally, in pursuing our questions of possible biological sources of these
gases, it will be of interest for us to examine our halocarbon data at particular
stations in collaboration with information provided by other AOS-94 colleagues. While halomethane concentrations may not be directly correlated
with bulk phytoplankton biomass, they might demonstrate some correlation
with the presence or species abundance of particular ice algae or phytoplankton identified by other researchers during the expedition.
69
1994 Arctic Ocean Section
C 2–C6 Hydrocarbons
Peter C. Brickell and Jan W. Bottenheim
The aft port bridge
of the Polar Sea ,
showing the tripleheaded air sampling
manifold leading
into a rear window
of the bridge superstructure.
In recent years there has been growing concern about human impact on the high Arctic regions. Light hydrocarbons
(C2–C6) in the environment include species that are primarily anthropogenic (for example, acetylene) and those that are
primarily biogenic in origin (for example, isoprene). These
species are of concern in the troposphere because they play a
major role in ground-level ozone formation in urban and urbanimpacted regions. The study of the light hydrocarbon composition of the high Arctic troposphere can provide one more
indication of human impact on the region. In addition, the
study of light hydrocarbons in background environments can
lead to a better understanding of photochemical reaction pathways occurring in these and other more polluted locations.
The high Arctic environment is generally free of the myriad
of local and regional anthropogenic hydrocarbon sources that
complicate the study of hydrocarbon photochemistry in southern continental
regions.
The goals of the light hydrocarbon measurement program during AOS-94
were to:
• Develop a reference light hydrocarbon database for the very high latitudes
in summer;
• Compare these data with those previously taken from land-based sites in
the high Arctic (for example, Barrow, Alaska; Alert, N.W.T., Canada; and
the Norwegian Arctic);
• Look for evidence of unusual patterns of chemical processes in the Arctic
troposphere; and
• Investigate the levels and patterns of anthropogenic light hydrocarbons at
very high latitudes and compare these with the levels of other anthropogenic tracers measured during AOS-94.
Air for light hydrocarbon analysis was sampled in two ways. We collected
air in electropolished stainless steel canisters using a battery-powered pump,
Peter Brickell and Jan Bottenheim are with the Atmospheric Environment Service in Downsview, Ontario,
Canada.
70
Contaminants
Acetylene Concentration [ppt (v)]
Ethane Concentration [ppt (v)]
and samples were stored for later analysis. Air was also drawn through a stainless steel sampling line mounted 22 m above the water line above the port
flying bridge. The line was routed to the laboratory, where samples were preconcentrated and then immediately analyzed by in-situ gas chromatography. Canisters could also be analyzed by this system for intercomparison measurements
with our laboratory in Toronto.
Because the location of the sampling line was fixed, this second method of
sampling could only be used when a substantial breeze (more than 3 m/s) was
blowing off the port side of the ship. This was necessary to avoid sampling
emissions from the vessel itself, and it essentially limited sampling to times
when the ship was stopped for science stations and when other sources of
contamination (such as helicopters) were absent. Suitable conditions for sampling were determined by monitoring the real-time output of carbon monoxide and condensation nuclei counter instru1000
ments. Sampling with the portable canister system was more flexible and allowed air to be
900
collected from any upwind location on the ship
or even on the ice if conditions warranted it. In
800
total 113 canister samples and 53 direct samples were collected; 40 of the canister samples
were analyzed with the on-board gas chromat700
ography system.
Canister data are available for the low600
70
80
90
80
molecular-weight alkanes and acetylene. DurPacific
Latitude (°N)
Atlantic
ing AOS-94 the mean ethane concentration
Ethane concentration vs. latitude during AOS-94.
from 73 to 80°N was 836 ± 68 pptv on the Pa100
cific side of the Arctic Ocean. This agrees well
with the concentrations observed during the
1988 ABLE 3A aircraft study based at Barrow,
90
Alaska. Farther north, from 81 to 87°N, ethane
concentrations dropped to 726 ± 36 pptv. From
80
87°N through the Pole and down to 80°N on
the Atlantic side of the Arctic Ocean, ethane
70
concentrations rose slightly to 765 ± 51 pptv.
Propane concentrations followed a similar pattern for the three areas. Acetylene concentra60
tions were initially 56 ± 6 pptv and rose slightly
to 64–65 pptv in the high-latitude and Atlantic50
side areas. The Pacific-side data agree well with
those from the 1988 ABLE 3A for Alaska, and
40
the high-latitude and Atlantic-side concentra70
80
90
80
Pacific
Latitude (°N)
Atlantic
tions compare very favorably with those for the
Acetylene concentration vs. latitude during AOS-94.
Norwegian Arctic.
71
1994 Arctic Ocean Section
AOS-94 light hydrocarbon concentrations and ratios compared with
those from other researchers for Alaska and the Norwegian Arctic.
Ethane
(pptv)
Pacific (73–80°N)
High Latitude (80–87°N)
Atlantic (87–90–80°N)
Alaska*
Norwegian Arctic†
Acetylene Propane Acetylene/ Propane/
(pptv)
(pptv)
Ethane
Ethane
836 ± 68
726 ± 36
765 ± 51
865 ± 59
56 ± 6
64 ± 7
65 ± 8
57 ± 17
69 ± 12
64 ± 8
87 ± 59
53 ± 15
0.061
0.088
0.085
0.066
0.084
0.089
0.113
0.061
1195 ± 27
67 ± 18
87 ± 30
0.056
0.073
* From Blake, D.R., D.F. Hurst, T.W. Smith, W.J. Whipple, T. Chen, N.J. Blake and F.S.
Rowland (1992) Summertime measurements of selected nonmethane hydrocarbons in
the Arctic and Subarctic during the 1988 Arctic Boundary Layer Expedition (ABLE 3A).
Journal of Geophysical Research, 97: 16,559–16,588.
† From Hov, O., S.A. Penkett, I.S.A. Isaksen and A. Semb (1984) Organic gases in the
Norwegian Arctic. Geophysical Research Letters, 11: 425–428.
Ratios of acetylene and propane to ethane concentrations were also calculated for this data set. The acetylene-to-ethane ratio for the Pacific side data is
consistent with the one for Alaska, but the Atlantic-side ratio is higher than
for the Norwegian Arctic. This difference is due to the lower AOS-94 ethane
results for the Atlantic side. Propane-to-ethane ratios are slightly higher than
those reported by other researchers for both the Pacific side and Atlantic side.
The difference on the Pacific side is attributable to the somewhat higher propane concentrations, and on the Atlantic side the difference is again due to
lower ethane concentrations.
The preliminary data from the light hydrocarbon canister sampling program agree well with work that has been done previously in the Alaskan and
Norwegian Arctic. The lower ethane concentrations on the Atlantic side of
the Arctic Ocean are probably attributable to increased distance from terrestrial sources. The ethane concentrations observed in the high-latitude portion
of the transect may be useful for determining the degree of aging of the air
mass encountered in this area. These light hydrocarbon concentrations will
provide additional data for estimating the background tropospheric volatile
organic compound levels used to input advective inflows for continental atmospheric modeling. In addition, although only data from the high Arctic regions
have been presented here, we collected hydrocarbon and some additional atmospheric data throughout the entire circumnavigation of the North American
continent during AOS-94. This has yielded a unique data set for assessing the
nature of continental and oceanic air masses, as well as providing an extended
latitudinal profile from 7 to 90°N for these atmospheric species. Finally, once
the Arctic data are available from all the compounds analyzed with the in-situ
gas chromatograph, it is expected that an improved understanding of background atmospheric chemical processes will have been derived from the sampling carried out on this unique expedition.
72
Cloud Radiation
— Cloud Radiation —
Atmospheric Radiation and Climate Program
Dan Lubin and Robert H. Whritner
One of the major physical components of climate change is the way in
which solar energy is redistributed in the Earth–atmosphere system. This subject also includes the simultaneous emission of thermal (infrared) energy from
the Earth’s surface and its partial entrapment by the atmosphere (the “greenhouse” effect). Globally well-mixed increases in carbon dioxide abundance are
believed by many to be enhancing the greenhouse effect and increasing the
global surface temperature field. This could have serious repercussions for Arctic
Ocean climate, as the Arctic Ocean surface exists for much of the year at
temperatures just below the freezing point of water. A small increase in surface
temperature could potentially have a large impact on the geographic extent of
Arctic sea ice, with resulting changes to the energy balance between the atmosphere and ocean.
Most of the scientific community’s insight into potential “global warming”
scenarios comes from large computer simulations called general circulation
models (GCMs). The GCMs are quite sophisticated but often suffer from a
lack of experimental input data and input physics from many remote regions
throughout the world, particularly the Arctic. AOS-94 offered a unique opportunity to deploy state-of-the-art atmospheric radiation budget measurement apparatus in the high Arctic and to allow them to gather data continuously for several weeks. This was the first high-Arctic expedition to deploy
these advanced optical instruments, and the large resulting data set should
enable better representation of the Arctic atmosphere in the GCMs.
The California Space Institute project consisted of three major components, all deployed aboard the Polar Sea. The first was a battery of broad-band
solar and infrared flux radiometers mounted above the pilothouse. Three Eppley Laboratory radiometers measured downwelling short-wave (0.28–2.8 µm),
near-infrared (0.78–2.8 µm) and middle-infrared (4–50 µm) radiation reaching the Arctic Ocean surface. A Biospherical Instruments radiometer measured
downwelling solar ultraviolet and visible radiation at 0.308, 0.320 and 0.380 µm,
as well as radiation in the intervals 0.580–0.680 µm (to match a satellite radiomDan Lubin is with the California Space Institute at the Scripps Institution of Oceanography in La Jolla, California, U.S.A. Robert Whritner is with the Arctic and Antarctic Research Center at the Scripps Institution of
Oceanography in La Jolla, California, U.S.A.
73
1994 Arctic Ocean Section
The California
Space Institute
experiment design
during AOS-94.
eter) and 0.400–0.700 µm (total photosynthetically active radiation). These
radiometers operated automatically and recorded data in one-minute averages
continuously throughout the cruise.
The second component consisted of the shipboard satellite tracking facility, the TeraScan system manufactured by the SeaSpace Corporation. In addition to providing weather and ice navigation for the expedition, the satellite
tracking enabled this project to measure energy reflected and emitted to space
at the same time that the shipboard instruments were measuring solar and
terrestrial radiation impinging on the Arctic Ocean surface. The TeraScan system was used to track NOAA polar-orbiting satellites, obtaining 1.1-km spatial
resolution images from the advanced very high resolution radiometers
74
Cloud Radiation
(AVHRR ), which measure radiation at five visible and infrared wavelengths. The
Defense Meteorological Satellite Program (DMSP) satellites were also tracked,
giving this project access to the special sensor microwave imager (SSM/I), which
was used to map sea ice along the expedition’s track. Throughout the cruise,
the Polar Sea TeraScan facility tracked between five and ten satellite overpasses
per day.
The third component consisted of a Fourier transform infrared (FTIR)
spectroradiometer operating in the middle infrared (5–20 µm) with a spectral
resolution of 1 cm–1 (Lubin 1994). FTIR data collection was coordinated
with the NOAA satellite overpasses, and a total of 178 sky scenes were studied
with the FTIR instruments. This instrument made detailed measurements of
radiation trapped by the atmosphere in the middle-infrared window (8–13
µm). Under clear skies the atmosphere is relatively transparent in this wavelength range, and a large portion of the heat given off by the ocean surface
escapes to space. Under cloudy skies, this window is mostly closed, meaning
that far less radiation escapes to space and the greenhouse effect is enhanced.
These greenhouse enhancements due to clouds are more than an order of
magnitude larger than what is expected from a doubling of carbon dioxide in
the atmosphere, so understanding the role of clouds in the atmospheric energy balance is critical before we can make meaningful “global warming” predic- AVHRR image
obtained from the
tions with GCMs.
shipboard TeraScan
During the summer of 1994, the atmosphere over the Arctic Ocean exhib- system on 4 August
ited a great deal of complexity, much more than is now represented in the 1994 during AOS94. Brighter shading
GCMs. A common occurrence was multiple-layered cloud systems. The ac- refers to lower cloud
companying figure is an image of terrestrial infrared radiation (10.5–11.5 µm) top temperatures.
emitted by the Arctic
ocean–atmosphere
0
system to space, ex–4
pressed in units of
–8
equivalent brightness
–12
temperature. At the
–16
time of this satellite
Deg C
overpass (4 August)
the Polar Sea was at
78°N, roughly in the
center of the image,
where there were three
distinct temperature
ranges in the cloud
fields corresponding
NOAA-12 AVHRR
to three distinct rangChannel 4 (Deep infrared)
04 August 1994 0057Z
es in cloud top height.
When the atmosphere
75
1994 Arctic Ocean Section
Atmospheric
emission spectra
measured by the CalSpace FTIR under
conditions of low
atmospheric opacity.
Atmospheric emission
spectra measured
by the CalSpace FTIR
under conditions
of high atmospheric
opacity.
76
contains a large amount of liquid or ice
water, as is the case with these multiplelayered cloud systems, a large portion of
the sun’s energy is reflected back to space
or absorbed by the atmosphere before
reaching the surface.
Two examples of atmospheric emission spectra from the CalSpace FTIR instrument are shown in the figure to the
left, under low atmospheric opacity.
Here the instrument is measuring terrestrial energy trapped by the atmosphere
and emitted straight back down toward
the ship. The middle infrared window exists between 800 and 1300 cm–1 on
this plot. The dotted curve, obtained under clear skies, shows that there is
very little energy being trapped and re-emitted by the atmosphere in the window, meaning that most is escaping to space. For wave numbers shorter than
800 and longer than 1300 cm–1, the atmosphere is largely opaque, and most
of the energy emitted by the Earth’s
surface at these wave numbers is always
trapped by carbon dioxide and water
vapor. The upper (solid) curve was obtained under a high ice cloud, and we
can see that in the window this cloud
results in nearly an order of magnitude
more energy at the ocean surface.
The figure to the left shows two
FTIR emission spectra obtained under
overcast skies (the most frequent sky
condition during AOS-94). The upper
(dotted) curve was obtained on 4 August, the same day as the AVHRR and
solar radiometer data discussed above. At the time of this measurement there
was so much liquid water in the atmosphere that the atmosphere radiated
energy to the surface almost like a perfect blackbody, as signified by the smoothness of this curve. In this situation, when we have a combination of high
cloud layers appearing very cold in the satellite data (that is, they are radiating
relatively little energy to space) and low cloud layers radiating nearly as much
energy as possible to the surface, at nearly the surface temperature, the greenhouse effect of the atmosphere is nearly at a maximum. The lower (solid) curve
was obtained under a single-layer stratus cloud. The middle infrared window is
almost but not quite closed. This is because the cloud base is several degrees
colder than the surface and because the cloud emissivity is less than one, mean-
Cloud Radiation
ing that the cloud does not contain enough liquid water to emit radiation like
a perfect blackbody. A doubling of carbon dioxide in the Earth’s atmosphere is
expected to increase the flux of infrared radiation at the surface by 3–4 W/m2.
The enhancements in surface infrared radiation related to changing cloud liquid water content and emissivity are on the order of tens of watts per square
meter.
The FTIR cloud emission spectra can be used to estimate the effective radius
of the cloud droplet size distribution (Lubin 1994), which in turn can indicate
whether or not continental air masses are influencing cloud microphysics.
Radiative transfer analysis of the AOS-94 cloudy sky emission spectra suggest
that 30% of the stratiform clouds sampled have effective droplet radii of 7 µm
or smaller, in which case they are probably influenced by continental air masses
and aerosol concentrations. By showing this type of microphysical phenomenon, along with the large variability in cloud optical depth that can occur (0–
50), this program has illustrated that the summer atmosphere in the high
Arctic is as dynamically and radiatively complex as that over any other continent or ocean.
REFERENCE
Lubin, D. (1994) Infrared radiative properties of the maritime Antarctic
atmosphere. Journal of Climate, 7: 121–140.
77
1994 Arctic Ocean Section
Aerosols
John D. Grovenstein, Richard Leaitch and Fred Hopper
10000
Concentration (cm–3 )
1000
100
10
1
208
212
Time series of
aerosol concentration for the AOS-94
expedition.
Aerosols, especially those that influence cloud microphysics (droplet size
spectra), are important in atmospheric research because they influence climate
directly by backscattering and absorption of incoming solar radiation and indirectly by affecting cloud albedo. Wigley (1989) suggested that the latter
effect could be the reason that the planet has not exhibited heating as predicted by global climate models of the
“greenhouse effect.” Generally
CN
climate models are poorly paramCCN (1% S)
eterized for aerosol and cloud miCCN (0.33% S)
crophysics, especially in the remote
PCASP
Arctic. Therefore, it is necessary to
measure these parameters to provide data sets for modelers and to
diagnose future environmental
change.
The figure at the left is a time
series of aerosol concentration
from AOS -94. The uppermost
dotted line is the condensation
nuclei (CN) concentration mea216
220
224
228
232
236
240
Day (1994)
sured by TSI models 3025 and
3022 condensation nuclei counters. This number represents the concentration of the finest nuclei (nucleation mode) with a radius of 0.003 µm to the
larger aerosols up to a radius of 3 µm. The uppermost solid line is the cloud
condensation nuclei (CCN) concentration active at 1% supersaturation. These
measurements were taken with an instantaneous CCN spectrometer introduced by Fukuta and Saxena (1979). For this study the spectrometer was operated at a range of 0.2–1.3% supersaturation. The spectrometer makes one
spectral sweep every 15 s. The middle dotted line is the CCN concentration
active at 0.33% supersaturation measured by the DH Associates cloud conJohn Grovenstein is with the Department of Marine, Earth and Atmospheric Sciences at North Carolina State
University in Raleigh, North Carolina, U.S.A. Richard Leaitch and Fred Hopper are with the Atmospheric
Environment Service, Downsview, Ontario, Canada.
78
Cloud Radiation
Concentration (cm– 3 )
densation nuclei counter. This instrument records the number of CCN active
at a single supersaturation (set at 0.33% for this study). The lowermost dotted
line is the large aerosol concentration (0.3–1.0 µm) measured with a Particle
Measuring Systems passive cavity aerosol spectrometer probe (PCASP-100X).
The instrument provides a histogram of aerosol concentration in 15 size ranges. The concentration from each size range is totaled to provide the concentration reported in the figure.
Sampling began on day 208 with instruments running on a continuous
basis. The concentration of aerosols measured by all instruments decreased
sharply upon entering the ice. The concentration of CN, CCN (active at 1%
supersaturation) and CCN (active at 0.33% supersaturation) “track” each other
through the time series, with the PCASP-100X showing this trend but not as
dramatically as the other measurements. Generally CCN concentrations in
maritime air masses rarely exceed 100 cm–3; however, concentrations above
100 cm–3 were measured over a time of days in the remote Arctic Ocean (days
218–224 and days 228–232). These large CCN concentrations also accompanied large CN concentrations, which in one instance (day 224) exceeded 7000 cm–3.
500
The concentrations of the larger aerosols,
CCN (1.0% S)
measured by the PCASP-100X and the CCN
CCN (0.33% S)
400
active at 0.33% supersaturation, never exceeded 100 cm–3 while we were sampling in the
ice. The observations of the largest CN and
300
CCN (active at 1% supersaturation) concentrations correspond to the lowest observed con200
centrations of the large aerosol with the
PCASP-100X. This suggests that the elevated
CN concentrations may be due to a local pro100
duction mechanism. The reduction of the largest aerosol removes a significant surface area
for the condensation of precursor gases. The
0
2
4
6
8
10
concentration of these gases increases until, by
Ice Coverage (tenths)
the process of gas-to-particle conversion, they
are converted into fine aerosol particles. Between days 218 and 224 the con- CCN concentration
two supersaturacentration of the finest aerosols are out of phase with the concentrations of the at
tions plotted against
largest aerosols; the peaks in concentration of one corresponds to the mini- ice coverage.
mums of the other. Although this scenario may not be the cause of the observed concentrations, the high concentrations of the precursor gases necessary have been recorded in the Arctic. The figure above shows the relationship
between ice coverage and CCN concentration, illustrating the possible production of CCN from precursor gases. When the gas supply is limited by ice
cover, CCN concentration decreases. Regardless of the source, the particles are
present and are modifying the climate of the remote Arctic.
79
1994 Arctic Ocean Section
REFERENCES
Fukuta, N., and V.K. Saxena (1979) A horizontal thermal gradient cloud
condensation nuclei spectrometer. Journal of Applied Meteorology, 18, 1352–
1362.
Saxena, V.K., and J.D. Grovenstein (1994) The role of clouds in the enhancement of cloud condensation nuclei concentrations. Atmospheric Research, 31,
71–89.
Twomey, S. (1977) The influence of pollution on the shortwave albedo of
clouds. Journal of Atmospheric Science, 34, 1149–1152.
Wigley, T.L.M. (1989) Possible climate change due to SO2 derived cloud
condensation nuclei. Nature, 339, 365-376.
80
Sea Ice
— Sea Ice —
Sea Ice Characteristics across the Arctic Ocean
Walter Tucker, Anthony Gow, Hazen Bosworth,
Erk Reimnitz and Debra Meese
The Arctic ice cover separates the ocean from the atmosphere, so it is a key
component in the exchange of heat, mass and momentum between the two.
The properties of the ice cover in summer are especially important, as this is
the period of maximum solar radiation. During summer the ice properties
become extremely variable, having changed from a highly compact, reflective
snow-covered surface during winter and spring to a mottled surface consisting
of melt ponds, bare ice and deteriorating snow with many open leads. Major
changes occur in the overall surface albedo, the ice cover warms accompanied
by draining brine and melting ice, and incorporated sediment and contaminants can be released. The amount of light penetrating into the ocean stimulates biological activity, because a major part of the Arctic Ocean food chain is
within a few meters of the ice.
The ice characterization component of AOS-94 consisted of surface albedo
measurements, melt pond characterization, snow depth surveys, aerial photography surveys, ice-borne sediment sampling and ice coring. Ice cores were
used for thickness, salinity, temperature, chemistry and structural analyses,
and samples were provided to associates for stable isotope measurements.
Visual observations and satellite imagery obtained on the section indicated
that the concentration of ice increased rapidly from 50–70% south of 72°N
to 90–100% for the remainder of the section until the marginal ice zone in
the Eurasian Arctic was reached. Ice thickness also increased with northward
progress from about 1 m in the first-year ice of the southern Chukchi Sea to
about 2.7 m at the North Pole, as verified from visual observations and ice
core measurements. With the exception of three ice cores obtained in the
Chukchi Sea, all cores on the section were collected from second-year or multiyear ice. The cores revealed thermally degraded ice near the surface above the
water level and extremely well drained ice below. Temperatures of the ice were
consistently near zero at the surface, increasing linearly to about –1.5°C at the
ice–water interface. Salinities were also consistent with previous measurements
of summer sea ice (Tucker et al. 1987, Eicken et al. 1995), being zero at the
Walter Tucker, Anthony Gow, Hazen Bosworth and Debra Meese are with the U.S. Army Cold Regions Research
and Engineering Laboratory in Hanover, New Hampshire, U.S.A. Erk Reimnitz is with the U.S. Geological
Survey in Menlo Park, California, U.S.A.
81
1994 Arctic Ocean Section
0
Mean Snow Depth (cm)
Ice CoreThickness (cm)
Depth (cm)
surface and increasing to 3–4‰ at depth. In general,
the thicker ice had greater salinities near the bottom.
50
Examination of the crystalline structure revealed
that 89% of the total ice sampled consisted of colum100
nar ice. Of the remainder, 9% consisted of granular
150
or frazil ice, and 2% contained platey ice, large platelettype ice that may have been associated with freezing
200
of under-ice melt ponds as suggested by Jeffries et al.
(1995). Much of the granular ice was associated with
250
previously deformed ice, identified by inclined colum300
nar crystals in adjacent sections typical of tilted blocks.
2
4
–2
–1
0 0
Salinity (‰)
Temperature (°C)
Surveys of snow depth were obtained at all ice samTemperature and
pling stations. South of 80° in the western Arctic, the ice appeared to be snow
salinity profiles for
covered, with very few bare ice spots visible. Close inspection of the snow
the same core from
cover characteristics revealed very large grains, close to 1 cm in diameter. We
the North Pole.
believe this indicates thermally deteriorated ice, rather than snow. Survey measurements showed mean depths of 6–13 cm of the deteriorated ice. Between
80° and 82°N metamorphosed corn snow was evident. In this region, mean
depths ranged from 10 to 15 cm. From 83° to 86°N depths of the old corn
snow decreased to 6–8 cm. North of 86° and into the eastern Arctic, new snow
Ice core thickness
was present, generally covering the old coarse snow, and the combined depths
and mean snow
were 6–15 cm. At all sites north of 80°, snow depths were variable, usually 0–
depth versus latitude during AOS-94.
5 cm on flat thin ice and up to 46 cm on the flanks of pressure ridges. North
The straight line is
of 85° it appeared that the melt season was complete, and the depth of the
the best-fit linear
regression. aged snow may represent the minimum for the 1994 ablation season.
Melt ponds in the Chukchi and southern Beaufort Seas were numerous, but farther north the ponds
400
began to freeze and eventually became snow covered.
300
Image analysis of aerial photographs obtained from
helicopter surveys allowed quantitative estimates of
200
the melt pond fraction. On 31 July at 76°N the total
pond
fraction was 12% and the lead fraction was
100
6%. On 13 August at 86°N the open pond fraction
0
was 3%, yet 10% consisted of identifiable frozen
20
ponds with a 2- to 5-cm ice cover. The lead fraction
had increased to 11%. At 88°N on 18 August no
15
open ponds were identified in the photographs, but
an areal fraction of 3% frozen ponds was evident.
The open water fraction remained at 11%. Measured
10
melt pond depths ranged from 20 to 60 cm. Six of
the 19 ponds sampled were saline and highly strati5
fied, with near zero salinity at the surface to 30‰ at
70
75
80
85
90
85
Pacific
Latitude (°N)
Atlantic
the bottom of the ponds. Saline ponds, though ap-
82
Sea Ice
100
Leads
Melt Ponds
Frozen Ponds
80
Ice
60
(%)
40
Relative areas of
ice and partitioning
of incident solar radiation for 31 July,
13 August and 18
August 1994. The
contribution from
different surface
conditions to the
disposition of the
solar radiation is
also show
20
0
7/31 8/13 8/18
Area Covered
7/31 8/13 8/18
Solar Radiation
Reflected
7/31 8/13 8/18
Solar Radiation
Absorbed in Ice
pearing to have solid bottoms, obviously had an established hydraulic link
with the ocean below. Cores through
the bottom ice verified this, showing
rotten ice with interconnecting channels. Colors of the ponds varied from
very light blue to deep dark green. The
color depended on the pond depth, the
condition of the bottom ice and biological activity. Chlorophyll a concentrations were found to be substantially
larger in green freshwater ponds than
in the light-blue ponds. The albedos
of the ponds also depended on depth
and color. Deep ponds with rotten bottom ice had albedos of 0.09; albedos were
as high as 0.3 for shallow light-blue ponds. Frozen snowcovered ponds farther north exhibited albedos of 0.8.
A two-stream radiative transfer model (Perovich 1990)
has been used to estimate the partitioning of incident solar
radiation into that reflected back to the atmosphere, that
absorbed by the ice, and that penetrating the ice to the
ocean or directly into leads. The results show a dramatic
decrease in the solar radiation absorbed into the ice after
18 August, when fresh, light snow covered the ice. The
model points out that most of the radiation absorbed by
the ocean comes from the absorption by leads, rather than
through the ice.
7/31 8/13 8/18
Solar Radiation
Transmitted to Ocean
Ice crystal structure
of multi-year ice
sampled at the
North Pole.
83
1994 Arctic Ocean Section
Tony Gow, Erk
Reimnitz, Bill
Bosworth and Terry
Tucker taking cores
of dirty ice.
Sediment was observed in and on the ice from the ice edge in the Chukchi
Sea to the North Pole. Near the ice edge, sediment covered an estimated 10–15%
of the surface of the ice. Farther north it covered less than 1% of the surface and
was extremely “patchy” in occurrence. Sediment was notably absent in the Eurasian Arctic, where it has been frequently observed on other expeditions.
Bulk samples of sediment were collected for analysis, and in many locations
ice cores were obtained through the dirty ice. Sediment entrained within the
ice was invariably associated with granular (frazil) ice formation. Frazil ice is
normally associated with turbulent growth conditions. Analyses of the particle sizes found primarily silt- and clay-sized particles; only 5.3% of the total
sediment collected was sand, while the proportions of silt and clay were 32.7%
and 62.0%, respectively. The few pelecipodes, ostracodes and foraminifera
found in the sediment indicate the shallow circum-Arctic shelves as the source
of the entrained sediment. The combined evidence indicates that sediment is
likely entrained into the ice by ice crystals scavenging suspended sediment
during stormy conditions on the continental shelves. Diffraction analysis of
the clay fine portion showed it to be composed of primarily illite and chlorite,
with smaller amounts of kaolinite and smectite. The smectite proportion increased
from near zero in the south to 10–15% in the more northerly samples.
Reverse trajectories calculated for the ice parcels from velocity fields produced by the International Arctic Buoy Program indicate that the shelf source
areas from the southernmost samples were the Canadian and Alaskan shelves,
while the East Siberian Sea appears to be the source of the more northerly
samples. Comparisons of organic carbon between the ice-borne sediment and
benthic sediments showed that three times more organic carbon (2.6%) was
present in the ice sediments than in the benthos (0.8%). It is likely that the
larger amounts in ice are due to biological activity. Conversely the benthic
sediments had ten times more carbonate than the ice sediments (10.3 vs. 0.9%,
84
Sea Ice
respectively), probably due to higher concentrations of foraminifera on the
sea floor. The visual estimates of sediment on the ice surface would indicate
that the amount of sediment being transported by the ice is small, yet because
it was observed across most of the Arctic Ocean, it is capable of transporting
and redistributing shelf sediments across the entire Arctic Basin.
A primary objective of the detailed ice-sediment study was to determine if
radiocesium was present within the ice-entrained sediment. In the ice-borne
sediments, 137Cs activities ranged from 4.9 to 73 Bq/kg (dry weight). Many
of the samples had 137Cs activities exceeding those found in benthic sediments in the deep basins or the shelves of the Beaufort, Chukchi or Bering
Seas, though the levels are far too low to be of concern to health. The highest
value (73 Bq/kg), found north of the Chukchi Sea, is comparable to levels
present in the sediments of the Yenesey and Ob River estuaries and the Kara
Sea. However, the three-year reverse trajectory indicated that the source area
for this parcel of ice was the offshore Banks Island region. Since there is no
known source in the Banks Island area, either the ice parcel was far older than
three years and had been incorporated elsewhere in the Beaufort Gyre or the
trajectory calculation neglected the possibility of easterly transport along the
Siberian shelf. Another remote possibility may be that radiocesium levels are
enhanced during the process of sediment entrainment into ice.
REFERENCES
Eicken, H., M. Lensu, M. Lepparanta, W.B. Tucker III, A.J. Gow and O.
Salmela (1995) Thickness, structure, and properties of level summer multiyear ice in the Eurasian sector of the Arctic Ocean. Journal of Geophysical
Research, 100: 22,697–22,710.
Jeffries, M.O., K. Schwartz, K. Morris, A.D. Veazey, H.R. Krouse and S.
Cushing (1995) Evidence for platelet ice accretion in Arctic sea ice development. Journal of Geophysical Research, 100: 10,905–10,914.
Perovich, D.K. (1990) Theoretical estimates of light reflection and transmission by spatially complex and temporally varying sea ice covers. Journal of
Geophysical Research, 95: 9,557–9,567.
Tucker, W.B. III, A.J. Gow and W.F. Weeks (1987) Physical properties of
summer sea ice in the Fram Strait. Journal of Geophysical Research, 92: 6,787–
6,803.
85
1994 Arctic Ocean Section
Measurements of Ice Mechanical Properties
F. Mary Williams
During AOS-94, ice mechanical properties were measured by the Institute
for Marine Dynamics. Williams (1994) gives details on the methods and results. The program was supported by Ship Safety, Canadian Coast Guard, as
part of a broad ship technology program.
Under the ship technology program, ice loads at three locations on the hull
of the Louis S. St-Laurent were monitored throughout the voyage, and significant events were recorded. Ship performance was documented by continuous
recording of propulsion system parameters, as well as ship speed and position.
The ice properties that influence hull loads and ship performance are the thickness, strength and density of the ice and the quality of the snow cover.
Ice temperature and salinity were measured at 10-cm intervals, and ice
density was measured at selected depths in vertical ice cores. Two cores were
taken at every science station in the ice using the Rapid-Core, a crane-deployed
coring device operated from the deck of the ship. Additional cores at sites
distant from the ship were taken using a hand corer. Often, average ice temperatures were –2°C, and average salinities were around 2‰. The ice contained
large brine channels, and brine in the upper layers had drained out.
Measurements of ice density from core samples are difficult at these temperatures. The result depends strongly on the amount of brine trapped in the
sample, which in turn depends on both the structure of the ice in the core and
sample handling. Most of the local density values were between 0.82 and 0.92
Mg/m3.
The inertial and buoyant forces of ice on the ship depend on the global, insitu ice density. This quantity, determined from freeboard measurements and
adjusted for the snow burden, was consistently between 0.92 and 0.93
Mg/m3.
A beam test is a direct measure of the flexural strength of the ice. When
logistics permitted, beam tests, in a standard size and configuration (Williams
and Parsons 1994), were carried out on the ice immediately after cutting the
samples. A typical result is a series of eight beams of columnar-grained ice at
–1.8°C, with an average flexural strength of 499 kPa. Some beam samples
were cold soaked and tested in the coldroom onboard the ship.
F. Mary Williams is with the Institute for Marine Dynamics in St. John’s, Newfoundland, Canada.
86
Sea Ice
Mary Williams
measuring the flexural strength of ice
beams.
When ice fails against the ship hull, the relationship between the average
ice pressure and the loaded area depends, in part, on the maximum pressure
sustained over actual contact areas, or hot spots. In materials that deform
plastically, this pressure, called the hardness, may be considered a material
property. Hardness was measured using a 136° pyramid Vickers Indenter.
Hardness decreased as contact area increased, from maxima near 60 MPa over
10–5 m2 to values near 15 MPa over 10–4 m2. The effects of temperature and
of work done on the ice are being investigated.
Since ice thickness varies with date and location, a ship-based measurement is not representative of the entire Arctic. However, such a measurement
is appropriate in an analysis of ship performance and hull loads. A video camera aimed at the ice surface near the starboard shoulder of the ship ran continuously throughout the trip. A computer-generated scale, calibrated at the ice
surface, overlaid the image on the video record and measured the thickness
and length of ice pieces turned up by the ship. Statistical results will not be
available until these data have been carefully analyzed.
To determine the ice crystal structure, rough thin sections of ice from some
of the cores and all of the beams were prepared in the coldroom and photographed through crossed polaroid filters. Most of the photos show highly
metamorphosed, unoriented, largely granular ice in a range of grain sizes. One
surprise was an ice sample with zero salinity and very large grains (>8 cm in
diameter) inadvertently taken from a concealed, refrozen melt pond.
Snow reduces ship performance through the inertial, buoyant and friction
forces it exerts on a moving ship. The water content and grain size of snow
affect imagery collected by satellite-borne microwave sensors by changing the
apparent brightness temperature of the ice surface. Thus, snow density and
type are key links between remotely sensed ice imagery and actual ship performance. Global snow density was measured in small full-thickness samples,
87
1994 Arctic Ocean Section
and the type was recorded qualitatively. Typical global
snow densities were 0.42 Mg/m3 for large-grained, wet
snow and 0.25 Mg/m3 for fine, new snow.
For evaluating the ship’s performance, and also for
interpreting the ice forces on the hull of the ship, the
Floe
Max
Mean
ice
and snow mechanical properties data were separated
size strength strength
(km) (kPa)
(kPa)
into four navigation zones. Up to latitude 80°N, there
was considerable surface melt and brine drainage. The
0.5
470
250
3.0
250
250
ice was porous and contained many flaws, allowing
1.0
500
500
relatively easy ship passage. However, mean ice tem0.5
600
300
peratures indicate that layers of intact, relatively cold
ice were present in some floes, with a risk of significant hull loads.
North of 80°, where air temperatures were lower, mean ice temperatures
were slightly higher than in the first zone. This apparent paradox is due to
melt surfaces advancing more rapidly than conduction isotherms and is recognized in icebergs (Diemand 1984). The ice was close to its melting point and
presented low strengths throughout the thickness.
The heavy ice at the highest latitudes, 88°N and beyond, was composed of
extensively damaged, worked and reconsolidated ice features. For this fairly
homogeneous ice, a higher ice strength applies to both ship performance and
load risk.
The transit was rapid and the sampling sparse from 90°N south to 85°N.
Hence, it is not certain where to place the boundary between zone 3 and zone
4. However, south of 85°N the ice was clearly thinner, less complex and of
lower concentration. The drained, low-salinity ice had begun to refreeze. The
completely frozen freshwater melt pond at Station 37 was an illustration.
Because of extensive flaws due to melting, the mean ice strength was low, but
the presence of solid, low-salinity ice pushed up load risk levels.
Ice properties in four navigation zones
during AOS-94. The maximum ice
strength is an index of maximum hull
loads, and the mean ice strength is an
index of ship performance.
Latitude
(°N)
70–80
80–88
88–90
85–81
Ice
cover
(10ths)
8 to 9+
9+ to 10
10
8 to 9+
REFERENCES
Diemand, D. (1984) Iceberg temperatures in the North Atlantic—Theoretical and measured. Cold Regions Science and Technology, 9(2): 171–178.
Williams, F.M. (1994) The Canada/U.S. 1994 Arctic Ocean Section—Ice mechanical properties measurements. Institute for Marine Dynamics: TR-1994-29.
Williams, F.M., and B.L. Parsons (1994) Size effect in the flexural strength of
ice. 13th International Conference on Offshore Mechanics and Arctic Engineering, Houston, Vol. IV, p. 15–22.
88
Geology and Paleoceanography
— Geology and Paleoceanography —
Sources of Ice-Rafted Detritus and Iceberg Tracks in the Arctic Ocean
Dennis A. Darby and Jens F. Bischof
The sources of ice-rafted detritus (dropstones) were determined by matching the elemental composition of iron oxide grains and percentages of grain
types in Arctic Ocean deep-sea sediment cores to potential sources around the
Arctic Ocean. This “fingerprinting” technique required prior characterization
of source areas in the Arctic providing debris that could be rafted into the
central Arctic Ocean by icebergs or sea ice. Eleven statistically unique source
areas were defined by grain type percentages and microprobe chemical analyses of thousands of individual iron oxide grains (Darby and Bischof 1996).
Erk Reimnitz collecting sediment
from the ice.
For the first time the sources of ice-rafted grains in the Arctic Ocean were
traced with a high level of statistical probability. This allowed us to reconstruct the ice drift tracks and the ocean surface currents in the past and to get
a better understanding of the nature and history of Arctic glaciations. Finally
the potential of pollutants being spread throughout the Arctic Ocean from
point sources on the Russian shelves can be assessed.
The major sources of detritus in 17 of the deep-sea cores thus far analyzed
(4 of 18 cores from the AOS-94 cruise and 13 from previous expeditions) are
the Banks and Victoria Island area and the Sverdrup Basin area around Ellef
Ringnes Island and northern Melville Island. The Mackenzie River basin conDennis Darby and Jens Bischof are with the Department of Geological Sciences at Old Dominion University in
Norfolk, Virginia, U.S.A.
89
1994 Arctic Ocean Section
1
2
Ellesmere Is.
Northern
Axel Heiberg Is.
3
Axel HeibergEllef Ringnes Is.
North
Slope
10
4
Melville and
Bathurst Is.
Devon Is.
6
5
ALASKA
8
7
Grinnell Peninsula
Lancaster Sound
Banks and
Victoria Is.
W
9
°N
70
°
70
Source areas for
Arctic ice-rafted
debris based on
statistically unique
grain-type content
and chemistry of
iron oxide grains.
Not shown is
another area in the
Kara Sea and the
102 till and glaciomarine sediment
sample locations
used to define
these areas.
GREENLAND
Mackenzie Delta
and Tributaries
°N
65
CANADA
tributes on average less than 10% to the ice-rafted detritus in the cores analyzed. Areas of existing ice caps such as Ellesmere Island, Axel Heiberg Island
and Greenland contribute even less to the western Arctic Ocean. About 25%
of the iron oxide grains in the studied Arctic Ocean core samples were from
unknown source areas. All glacial sources except those of the Barents Shelf and
adjacent land masses were sampled to varying degrees of thoroughness. We
suspect that many of the iron oxide grains from presently unknown sources
(the average from 17 cores is 26%) may have been rafted by sea ice from the
Russian shelves. This has serious implications because of the modern pollution
from radioactive dumps and other pollutants attached to sediment in parts of this
shelf area.
Down-core changes in source area contributions show that cyclic surging of
ice sheets and ice caps has occurred at least throughout the last 780,000 years
in the Arctic. The cyclicity is less than about 30,000 years and probably less than
10,000 years during glacial intervals, but because of the lack of a more detailed
chronostratigraphy in the Arctic cores, the frequency cannot be resolved further.
Pulses of ice rafting from different sources in 14C-dated Holocene sediments
(<10,000 years old) of the central Arctic Ocean lasted less than 2,000 years.
The Laurentide ice sheet that calved into the Arctic Ocean from Melville or
Banks Island to the Mackenzie Delta area coexisted with several small ice caps or
possibly a larger ice sheet over the Queen Elizabeth Islands. This is based on the
discovery of detritus from both ice masses in the same 0.5- to 1-cm-thick core
samples.
The last glaciation in the Queen Elizabeth Islands transported little ma-
90
Geology and Paleoceanography
terial from the interior areas, inland from the Arctic
Ocean, such as the Precambrian Shield. Grain-type
percentages in glacial deposits on and around these
islands closely match rock types of local formations.
Heavy mineral and iron oxide grains show less-clear
affinities to local rock types but generally corroborate the local nature of tills and glaciomarine sediments in the Queen Elizabeth Islands.
Today’s Beaufort Gyre circulation in the western
Arctic Ocean, a clockwise ice drift, cannot explain
the observed compositional differences between widely spaced core locations. The data obtained thus far
suggest that the surface circulation in the western
Arctic was toward Fram Strait, even along the Canadian Arctic coast during glacial intervals. This means
that surface currents were opposite or perpendicular
to the southwestward currents today within a couple
of hundred kilometers of the Canadian Arctic coast. Thus large numbers of
icebergs moved northeastward near the coast and into the North Atlantic during glacial maxima, while a thick floating ice cap blocked or greatly inhibited
icebergs from reaching the central and western parts of the Arctic Ocean. This
is further supported by the slower sedimentation rates in these central areas.
Unusual magnetite spherules (40–60 µm) with about 6–18% zinc oxide
and 18% nickel oxide were found at over 30 sites in the Queen Elizabeth
Islands and in several Arctic Ocean cores in sediment as old as 780,000 years.
Iron meteorites lack zinc because of its volatility at temperatures of atmospheric entry, so an impact event in zinc-bearing limestones such as the Haughton Astrobleme (~22 million years ago) is still considered to be a likely explanation for such spherules. However, a detailed search for these spherules in
ejecta from the Haughton Astrobleme on Devon Island was negative. Thus, if
these spherules were formed by such an event, it is yet to be discovered in the
Queen Elizabeth Islands.
Thick
Ice
Iceberg drift tracks
and surface currents
for earlier glacial
maxima in the western Arctic Ocean
based on dropstones and iron
oxide grains. The
zone of thick ice
inhibits iceberg drift
and causes low
sedimentation rates.
Arrows depict iceberg drift from the
Laurentide Ice Sheet
(open arrows) and
glaciers from the
Queen Elizabeth
Islands (solid
arrows). Core locations used for this
reconstruction are
shown as black dots.
REFERENCE
Darby, D.A. and J.F. Bischof (1996) A statistical approach to source determination of lithic and Fe oxide grains: An example from the Alpha Ridge, Arctic
Ocean. Journal of Sedimentary Research, 66: 599–607.
91
1994 Arctic Ocean Section
Late Quaternary Paleoceanography of the Canada Basin,
Central Arctic Ocean
William M. Briggs and Thomas M. Cronin
This project is based on quantitative analysis of the ostracodes present in
seafloor boxcores and piston cores collected during AOS-94. Ostracodes are
small, bivalved crustaceans whose shells, or valves, are made up of calcium
carbonate in the form of the mineral calcite, which also contains trace amounts
of magnesium.
Seafloor sediments of the central Arctic Ocean ( CAO) contain two types of
deep-sea ostracodes: cladocopids and podocopids. Cladocopid ostracodes are
extremely abundant in the CAO, where they are represented by about 13 species
of the genus Polycope. Cladocopids are part of the epifaunal bottom community, and they can swim for short distances just a few centimeters above the sea
bottom. The podocopid ostracodes of Arctic Ocean sediments, with one exception, are bottom-dwelling species, some living at the sediment–seawater interface
(epifaunal) and others living in the substrate just below the interface (infaunal).
The exception is the genus Acetabulastoma, which has a lifestyle of commensalism on at least two species of gammarid amphipods that are part of the
under-ice community in Arctic marine environments. Whether due to the
death of the host amphipod species or the release of ostracode shells from the
host species by accidental detachment, death or molting, the shells of Acetabulastoma eventually sink through the water column and come to rest on the seafloor, where they become part of the ostracode bottom fauna. Their shells are
therefore not indicative of the ostracode assemblages used to characterize certain water masses. The presence or absence of Acetabulastoma in downcore
ostracode assemblages can be used as a proxy indicator of the magnitude and
extent of ice cover in the CAO. This has important implications for CAO icecover history and its linkages to paleoceanography, paleoclimatology and global change.
Many ostracodes in the marine realm live within narrowly defined environmental tolerance limits, and their distribution on the seafloor is governed
by variables such as the temperature, salinity, oxygen concentration and nutrients in the overlying water column and the type of sediments on the seafloor.
William Briggs is with the Institute of Arctic and Alpine Research at the University of Colorado at Boulder,
Colorado, U.S.A. Thomas Cronin is with the U.S. Geological Survey at Reston, Virginia, U.S.A.
92
Geology and Paleoceanography
Studies of ostracodes in surface sediments
from piston core and boxcore tops, collected mainly from the Eurasia Basin of
the Arctic Ocean and analyzed using
multivariate quantitative and clustering
techniques, have shown that many ostracode species that form assemblages in the
Arctic Ocean have distinct bathymetric
ranges that are related to the depthstratified water masses of the present-day
water column. Thus, we are able to recognize assemblages of ostracodes that are diagnostic of:
• Polar surface water (0–100 m), below which lies a 100-m-thick halocline layer;
• Arctic intermediate water (Atlantic water) (200–800 m); and
• Arctic Ocean deep water (to 4000 m or more).
These water masses are in themselves easily differentiated from one another
because each has a characteristic temperature–salinity signature, which is related
to water density, which in turn, determines their position in the stratified water
column. We, therefore, are able to recognize and “calibrate” these modern analog
ostracode assemblages with what is known of the physicochemical properties of
each water mass or subdivisions of the water mass into upper and lower parts.
Thus, “depth-related” ostracode assemblages in modern-day Arctic seafloor sediments are proxy indicators of water mass type. Moreover, downcore changes in
ostracode assemblages, when compared to the modern analog coretop assemblages by a quantitative method called the modern analog technique (MAT),
will result in a proxy record of the water-mass history over a basin, abyssal
plain, ridge, rise or plateau in the deeper (≥4 km) to shallower (~1 km) parts of
the Arctic Ocean during late Quaternary time.
We have found:
• Well-preserved ostracodes and good biostratigraphies downcore in boxcores from the Mendeleyev and Lomonosov Ridges and slopes;
• Ostracodes in 18 boxcore tops; and
• Well-preserved adult specimens of the deep-sea ostracode genus Krithe to
be used in shell-chemistry studies.
The longest of the 18 boxcores is 46 cm long. On average, sedimentation rates
are on the order of 1–2 cm per 1000 radiocarbon years (1 kyr) in the CAO for
the Holocene (the last 10,000 kyr). Sedimentation rates during the last glaciation have been variously estimated at 0.1–0.2 cm/kyr up to 0.5 cm/kyr, based
on accelerator mass spectrometry (AMS) 14C dating. Thus, the ages of the preHolocene sections of the boxcores in all likelihood span all of the last glaciation, which dates from approximately 70–10 kyr ago, and may be older. All of
the boxcores, then, must record the time of the last glacial maximum (approximately 18 kyr ago) through to the present.
Liz Osborne processing seafloor
cores in the Polar
Sea core laboratory.
93
1994 Arctic Ocean Section
Our objective is to study the ostracodes in boxcore sections from the last
glacial maximum through Termination 1a and 1b to the present. Termination
1a marks the beginning of the last deglaciation, dated at 15.7 kyr ago (16,650
calendar years B.C.), and Termination 1b marks the end of the last glacial–
deglacial transition, dated at 7.2 kyr ago (6,000 calendar years B.C.). Modern
surface and deep-sea circulation patterns and seasonal ice-free conditions are
believed to have been established in the northern North Atlantic and Arctic
Oceans following Termination 1b. These changes are in direct response to the
drawdown and final collapse of the great Northern Hemisphere ice sheets (the
Laurentide and the Fennoscandian). Quantitative analysis of the downcore
ostracode assemblages by the MAT will record upslope and downslope
migrations of ostracode assemblages in response to changing oceanographic
conditions due to changes in circulation following the decay and collapse of
these ice sheets.
To date, we have sampled five of the eighteen boxcores from sites on the
Mendeleyev Ridge and slope, the Lomonosov Ridge and slope, and the Pole
Abyssal Plain. All of these cores have well-preserved ostracodes, except for the
one from the Pole Abyssal Plain, which has poorly preserved ostracodes in the
top few centimeters downcore and no calcareous faunas of any type farther
downcore. The well-preserved downcore ostracodes will greatly aid in the paleoceanographic history of the Mendeleyev and Lomonosov Ridges and other
ridge areas of the Arctic Ocean. High-resolution downcore AMS 14C and oxygen isotope records, which will be made available by Glenn Jones and William
Curry of the Woods Hole Oceanographic Institution, will be indispensable to
the project. These records, when augmented by the ostracode biostratigraphy,
will allow us to pinpoint the timing of paleoceanographic events in the Arctic
Ocean over the last few centuries and millennia, and these data will help predict future change. We are separating out adult specimens of two species of
the deep-sea ostracode genus Krithe for use in downcore single-valve geochemical analyses by Paul Baker and Gary Dwyer of Duke University, who, in collaboration with Thomas M. Cronin, are developing geochemical proxy tools to
determine paleotemperatures and other physicochemical variables in the deep
ocean based on the shell chemistry of Krithe. New distribution records of the
ostracodes in coretop samples will allow us to fine tune the Arctic Ocean
Database, and these data will greatly enhance the resolution of the MAT. We
will also examine selected piston cores for much older paleoceanographic and
paleoclimatic records when samples from these cores become available.
94
Geology and Paleoceanography
Elemental and Isotope Geochemistry of
Sediment from the Arctic Ocean
Bryce L. Winter, David L. Clark and Clark M. Johnson
Elemental and radiogenic isotope studies of marine silicate sediment have
greatly increased our understanding of the lower-latitude and southern oceans.
However, no comprehensive study had been conducted in the Arctic Ocean.
Elemental and radiogenic isotope compositions of marine silicate sediment
are powerful tools for understanding the sediment source region, including its
location, general lithologic composition, age and crustal depth of exposure.
Upon identifying the source location and using sediment compositional variations to establish distribution patterns, it may be possible to reconstruct sediment transport pathways and infer transport mechanisms. This may provide
independent information concerning paleoceanographic or paleoatmospheric
circulation patterns and contribute to better paleoclimate reconstructions.
Surface sediments collected along the AOS-94 track (Mendeleyev Ridge,
Makarov Basin, Lomonosov Ridge, Amundsen Basin and Nansen Basin) have
been analyzed for major and trace elements via instrumental neutron activation
and x-ray fluorescence. We are completing Rb–Sr, Nd and Pb isotope analyses
via thermal ionization mass spectrometry. We have analyzed the major and
trace element compositions for 20 other deep-ocean sediments (Canada Basin,
Northwind Ridge and Alpha Ridge), 3 sea ice samples and 19 samples of
sediment from rivers and shelf areas that are potential source regions (Queen
Elizabeth Islands, northern Canada, Kara Sea, Ob River, Yenisey River and
Pechora Sea).
Initial examination of the elemental data shows that all deep ocean sediment, except that from the Canada Basin, has much higher concentrations of
transition elements, such as Co and Ni, than does sea ice sediment and the
sediment samples from potential source regions. Transition elements are concentrated in hydrogenous oxide coatings, which accumulate on sediment particles at the sediment–water interface in marine settings. Sediment from the
Canada Basin is deposited by turbidity currents at much higher sedimentation
rates than other areas of the central Arctic Ocean; hence, there is less accumulation of hydrogenous oxide coatings on sediment from the Canada Basin.
Sediment from the Ob and Yenisey Rivers and the Kara Sea have much
higher concentrations of compatible elements (such as Cr and Sc) than all the
Bryce Winter, David Clark and Clark Johnson are with the Department of Geology and Geophysics at the
University of Wisconsin-Madison in Madison, Wisconsin, U.S.A.
95
1994 Arctic Ocean Section
500x
Analytical Precision
other sediments that have been analyzed.
This is consistent with the high concentraSeawater
tions of smectite in this region and indi1
cates that the extensive Mesozoic basalt
Oxide
Silicate
complexes of the adjacent continental land
Fraction
Fraction
mass are important sources of sediment to
this shelf region. However, these rivers and
2
the Kara Sea shelf in general cannot be important sources of sediment for the central
Arctic Ocean.
3
Late Cenozoic sediments on the Alpha
Ridge
in the central Arctic Ocean (~5 m
4
thick)
were
deposited at very low sedimenta5
0.705
0.710
0.715
0.720
0.725
tion rates (~1 mm/ky) and can be separated
Sr/ Sr
into two distinct sedimentary packages based
Sr isotope varia- on lithology. The lower package (~5–2.4 Ma) is composed of silty lutites that
tions of components
of Late Cenozoic are interpreted to have been deposited by sea ice. The upper sedimentary packsediment from the age (~2.4–0 Ma) is composed of alternating sandy and silty lutites and has
Alpha Ridge, central glacial dropstones occurring throughout the sequence. The younger cyclic seArctic Ocean. The
components that quence is interpreted to have been deposited by glacial ice; the coarse layers
were analyzed in- were deposited during glacial maxima and deglaciation, whereas the fine include the oxide frac- tervals were deposited during interglacial periods. We have analyzed detrital
tion of ferromanganese micronodules silicate material, planktonic foraminifera and the diagenetic (oxide) fraction of
(solid circles), the ferromanganese micronodule (50–300 µm) separates throughout a composite Late
silicate fraction of
Cenozoic sedimentary sequence for variations in Nd, Sr and Pb isotopes and rare
ferromanganese miearth elements. The oxide fractions of Fe–Mn micronodule separates were isocronodules (open
circles) and bulk sili- lated using a chemical reductant. The foraminifera and the diagenetic fraccate sediment
tions record the isotope variations of Arctic seawater.
(open triangles).
The Sr, Nd and Pb isotope compositions of the siliciclastic fraction are
homogeneous during the time of sea ice sedimentation (~5–2.4 Ma), whereas
87Sr/86Sr and 206Pb/204Pb ratios progressively increase and 143Nd/l44Nd ratios
decrease during the time of glacial sedimentation. We interpret these isotope
variations to indicate a progressive change in the source of sediments to the
central Arctic Ocean beginning at the time of initiation of continental glaciation (~2.4 Ma). All the isotope systems are remarkably consistent and indicate
that the sediment source region during glacial sedimentation (~2.4–0 Ma)
had a greater supracrustal component and/or an older average age relative to
the source that supplied sediment during the time of sea ice sedimentation
(~5–2.4 Ma). The isotope data are consistent with derivation of the older
(~5–2.4 Ma) sediment entirely from the Siberian shelf, whereas the Canadian
Island region became a progressively more important source of sediment since
~2.4 Ma. The general increase in the amount of coarse sediment since ~2.4
Ma is consistent with this hypothesis. We intend to further refine and substantiate sediment source regions by analyzing circum-Arctic river and shelf
sediments for isotope variations.
87
96
86
Glacial Sediment
Sea Ice Sediment
Gilbert
Gauss
Age (Ma)
Matuyama
Brunhes
0
Ship Technology
— Ship Technology —
Real-Time Remote Sensing for Ice Navigation
Caren Garrity, Dan Lubin and Réné O. Ramseier
AOS-94 explored areas never before studied by surface ships. An investigation of historical ice conditions indicated that we could expect an average of
83 ± 11% ice concentration along the planned route to the North Pole. A
major advantage of this expedition was the installation onboard the Polar Sea
of a TeraScan receiver and processing system developed by SeaSpace Corporation. The system was capable of real-time reception and processing of imagery
from the advanced very high resolution radiometer (AVHRR) on NOAA satellites as well as the special sensor microwave imager (SSM/I) data from the
Defense Meteorological Satellite Program (DMSP) satellites.
The AVHRR imagery is in the visible and infrared wavelengths, and these
sensors are useful for real-time weather information. Their usefulness for monitoring ice motion on this voyage was extremely limited due to the nearly constant cloud cover and considerable fog. During AOS-94, 5.3% of the transit days
to the North Pole were nearly cloud free, and 17 days were free from fog. To be
useful for ice navigation, a satellite sensor needs to “see” through clouds and fog.
Sensors using the microwave frequency range such as the SSM/I have this capability.
Three SSM/I algorithms were used to map sea ice during AOS-94: NASA
Team (NASA, U.S.), AES (Canadian Atmospheric Environment Service) and
85 GHz (Scripps, U.S.). The former two algorithms provide coarser-resolution
ice maps by combining the lower-frequency channels of the satellite sensor (19
and 37 GHz). Previous comparisons of these are summarized, including an
error analysis, in Steffen et al. (1992). The 85-GHz ice concentration maps
have twice the resolution (12.5 km), and the new 85-GHz algorithm is summarized in Lomax et al. (1995). The reported error for derived total ice concentrations during the winter is approximately 9% for the NASA Team and AES
algorithms. This error is due to signature uncertainty and the uncertainty in
atmospheric parameters, including instrument noise effects. As a result of this
experiment the 85-GHz algorithm has been evaluated (Lubin et al. 1996)
While AOS-94 was useful for comparing the ice concentrations derived
from the three algorithms, it is difficult to “validate” the sea ice algorithms,
since observing ice from the bridge of a ship is somewhat qualitative and the
visibility is limited to a small area. The visibility was estimated to be from 0.05 to
Caren Garrity and Réné Ramseier are with the Microwave Group–Ottawa River, Inc., in Dunrobin, Ontario,
Canada. Dan Lubin is with the California Space Institute at the University of California–San Diego in La Jolla,
California, U.S.A.
97
1994 Arctic Ocean Section
120
Total Ice (%)
100
80
60
40
210
Ice concentration
along the Polar
Sea’s track to the
North Pole.
98
10 nautical miles during the
transect. Often the ice concentrations were overestimated, since the farther one
looks towards the horizon,
the less open water can be
seen. When the ship is progressing slowly through a
vast old ice floe, for example,
AES
85 GHz
NASA
Visual
from the ship the ice concentration could appear to
215
220
225
230
Julian Day
be 100%.
The total ice concentration along the ship’s track was derived from each of
the algorithms and estimated from visual ice observations. The average visually
estimated ice concentration was 93% along the total ship’s track (A.R. Engineering, and Science and Technology Corporation 1994). The AES and 85-GHz algorithms show an average of 88% and 84%, respectively; the NASA team algorithm, which appears to underestimate the ice concentration, averaged 78%.
The microwave sensors are influenced by cloud liquid water content and
snow wetness, which cause an increase in the brightness temperature detected
by the sensors. The NASA Team and AES algorithms, using the lower frequencies, are less sensitive to atmospheric moisture than the 85-GHz algorithm.
The derived ice concentrations are significantly affected by the snow wetness,
however (Garrity 1991, 1992). For example, the 85-GHz derived ice concentrations can be as large as 110%. When using the 85-GHz algorithm over regions
of lower ice concentration, the reference polarizations in a given image must
be chosen with care because there the polarization-based algorithm is more
sensitive to cloud opacity and can easily and substantially underestimate the
ice concentration (Lubin et al. 1996). However, near the ice edge, the 85GHz derived ice concentrations were closer to visual observations than the
conventional algorithms were, most likely due to better resolution. Comparison of 85-GHz brightness temperatures measured from space with both the
lower-frequency measurements and with the shipboard observations shows
that much of the information about surface properties, including snow wetness and volume scattering in multiyear ice, is contained in the 85-GHz signal, despite the higher atmospheric opacity.
Using the 85-GHz algorithm, ice concentrations greater than 100% are reduced to 100% and a colored ice map is produced for operational use. The influences of the atmosphere and snow wetness on derived ice concentrations are
less than 10% for the high ice concentrations encountered during AOS-94, so
this is not a critical problem. For determining total ice concentration during summer in the high Arctic, the new 85-GHz algorithm is as good as the conventional
lower-frequency algorithms, if not better because of the doubled resolution.
Ship Technology
The 85-GHz SSM/I ice product
aided navigation and planning of
scientific station stops on a daily
basis. For example, the ship was rerouted to the west of 180° because
of the 100% total ice concentration
to the east. The 100% ice concentration areas were consistent during
the experiment, and the consistency
was confirmed using the three algorithms and helicopter surveys. The
SSM/I ice maps provided an overview, which aided the process of deciding how to proceed from the North Pole. The SSM/I and AVHRR data
provided ice and weather information during AOS-94 and met the criteria for
being operational, that is, timeliness, coverage and interpretation. It was clearly demonstrated that the ships could easily reach their goal by having a miniice center in the high Arctic, where communication is difficult and expensive.
Caren Garrity
measuring snow
wetness.
REFERENCES
A.R. Engineering, and Science and Technology Corporation (1994) Hull/
ice interaction loads measurements on-board the Louis S. St-Laurent during
the 1994 trans-Arctic voyage: Trip report and data summary. Submitted to
Fleet Systems, Canadian Coast Guard, by A.R. Engineering, Calgary, Alberta,
Canada, and Science and Technology Corporation, Columbia, MD, U.S.A.
Garrity, C. (1991) Passive microwave remote sensing of snow covered floating
ice during spring conditions in the Arctic and Antarctic. Doctor of Philosophy, Graduate Programme in Earth and Space Science, York University, North
York, Ontario, Canada.
Garrity, C. (1992) Characterization of snow on floating ice and case studies of
brightness temperature changes during the onset of melt. In Microwave Remote
Sensing of Sea Ice. Geophysical Monograph 68, p. 313–326.
Lomax, A.S., D. Lubin and R.H. Whritner (1995) The potential for interpreting total and multiyear ice concentrations in SSM/I 85.5 GHz imagery.
Remote Sensing of Environment, 54: 13–26.
Lubin, D., C. Garrity, R.O. Ramseier and R.H. Whritner (1996) Evaluation
of the special sensor microwave imager 85.5 GHz channels for total sea ice
concentration retrieval during the 1994 Arctic Ocean Section. Submitted to
Remote Sensing of the Environment.
Steffen et al. (1992) The estimation of geophysical parameters using passive
microwave algorithms. In Microwave Remote Sensing of Sea Ice. Geophysical
Monograph 68, p. 201–231.
99
1994 Arctic Ocean Section
Ship Technology Program
Larry Schultz and Rubin Sheinberg
Polar Sea
breaking ice.
The AOS-94 ship technology program consisted of two parts. One part
was concerned with measuring the icebreaking capability of the two icebreakers,
the USCGC Polar Sea and the CCGS Louis S. St-Laurent, while transiting
high-Arctic ice conditions. The other part involved measuring the loads imposed
on the hull of the Louis S. St-Laurent due to impact with the ice.
Icebreaking performance data typically define the power required for an
icebreaker to break a given thickness of uniform ice at a given speed. Plans were
made to perform dedicated performance tests in a range of uniform conditions if
such were encountered. No uniform ice conditions suitable for performance testing were encountered, however, in the entire expedition.
In contrast, trafficability data provide information on the ability of an
icebreaker to transit from
point to point in a given
geographic area in a realworld mix of ice conditions. Ice trafficability
data were recorded hourly during the entire time
the ships operated in ice,
resulting in about 500
hours of data on ship propulsion, environmental conditions and ice conditions. The data on ice conditions included the classification of the ice as first
year, second year or multiyear; the lead width; the average and maximum floe
size; the concentration of the ice cover broken down in increments of thickness; the average and maximum thickness; the pressure ridge encounter rate;
and the average and maximum sail height of the pressure ridges. The environmental data included the snow depth and type, a characterization of the ice
pressure, and the diameter and concentration of melt ponds. Data on openwater performance and seakeeping were collected during the open-water transit legs of the expedition.
Larry Schultz is with Advanced Marine Enterprises, Inc., in Arlington, Virginia, U.S.A. (He was formerly with
Science and Technology Corporation in Columbia, Maryland.) Rubin Sheinberg is with the U.S. Coast Guard in
Baltimore, Maryland, U.S.A.
100
Ship Technology
Finally, the performance study also included an analysis of the shipboard
science spaces and equipment onboard both ships, based on observations and
interviews with the scientists. The trafficability and performance data will
contribute to the knowledge base available for the design of future icebreakers
in terms of ship resistance and powering and in terms of a realistic mix of ice
conditions and operating modes for high-Arctic transit. Since the expedition
completed a full transect of the Arctic Ocean from the Pacific to the Atlantic
via the North Pole, the data recorded on ice conditions and environmental
conditions will be extremely valuable in planning future high-Arctic icebreaker
expeditions.
The ice impact loads portion of the program is part of an ongoing joint
effort between the Canadian and U.S. Coast Guards to improve ice load impact
criteria for ice-going ships. Collaborative work between the two governments
to measure the pressure distribution on the hull of an icebreaker during ice
impact incidents started in 1982 with a bow measurement panel on the Polar
Sea. Since then data have been collected and analyzed from five deployments
of the Polar Sea in both the Arctic and the Antarctic, one extended deployment of the Swedish icebreaker Oden to the Arctic Ocean, and one deployment of the Nathaniel B. Palmer to the Weddell Sea in Antarctica in winter.
The measurements have provided the first insight into the magnitudes of local
ice impact pressures and how they vary with time, contact areas and ice conditions. The data collected on the Louis S. St-Laurent during AOS-94 focused
on the relative magnitude of forces and pressures on three areas of the hull
structure: the bow, the shoulders and the bottom. Additionally, vessel maneuvering and powering data were collected for characterizing the vessel operations during the recorded hull–ice impact events. Data were also gathered on
the environmental and ice conditions during the events.
Data for 3217 impact events were recorded on the data acquisition system.
The system was configured such that an impact on any single measurement
area could trigger an event. In some cases, simultaneous impacts were recorded
on two or all three of the measurement areas. The greatest number of impacts
were recorded at the bow, as would be expected. Side impacts were the next
most frequent, followed by bottom impacts. If the multiple-impact cases are
taken into account, the total number of recorded impacts is 4037. Preliminary analysis has shown that the magnitude of the forces and pressures is consistent with previous measurements in multiyear ice. Ongoing data analysis will
determine data trends and correlate impacts with ship operating and ice conditions. Extreme load profiles will then be developed and relationships established for the frequency, magnitude and pattern of the loads on the three
instrumented hull areas. The relationships will then be compared with those
specified in the Revised Canadian Hull Construction standards, and recommendations will be made as appropriate.
101
1994 Arctic Ocean Section
Hull–Ice Interaction Load Measurements
on the CCGS Louis S. St-Laurent
David Stocks
A strategic objective of the Canadian Coast Guard Northern Operations
Programme is to support the scientific community in their requirements for
platforms to conduct investigations in the Canadian Arctic. A further departmental objective, with respect to ensuring safety and environmental protection
in the Canadian Arctic, requires that regulations be developed for ships operating in these regions.
The U.S. and Canadian Coast Guards have, over the last decade, cooperatively executed an extensive program of ice–ship hull interaction investigations on ice-strengthened ships. This initiative was stimulated by the joint
need to develop structural standards for the design of ice-strengthened ships
and has, for the most part, focused on the most highly loaded area of the ships’
hull, the bow. Several ships have been instrumented for dedicated ice trials of
their bow areas, including the CCGS Louis S. St-Laurent and the USCGC
Polar Star. More recently the USCG and CCG combined their resources to
conduct experiments on the Swedish icebreaker Oden during its 1991 North
Pole voyage and the American icebreaker the Nathaniel B. Palmer during its
1992 voyage to the Antarctic.
The objective of this component of AOS-94 was to enhance the body of
knowledge with respect to the structural response of ice-strengthened ships,
specifically in areas of the ship’s hull never before examined, such as the ship’s
side aft of the bow and bottom forward, and in areas of Arctic ice never before
encountered by Western vessels. The benefits of this work are two-fold; first,
to aid in the development and verification of the Arctic Shipping Pollution
Prevention Regulations (structural standards), and second, to demonstrate and
prove the capability of the platform to support the scientific missions.
The project was jointly sponsored by the CCG and USCG, and contracts
were let to A.R. Engineering Ltd., Calgary, Alberta, Canada, and Science and
Technology Corporation, Columbia, Maryland, U.S.A. Three phases were contracted:
• The installation of instrumentation onboard the ship;
• The acquisition of data during the voyage; and
• The synthesis and analysis of data after the voyage.
David Stocks is with the Canadian Coast Guard in Ottawa, Ontario, Canada.
102
Ship Technology
The Canadian contractor was primarily responsible for the first phase, the
second phase was a joint responsibility, and the third phase is being completed,
primarily by the U.S. contractor.
A hull loads data acquisition system was installed on the CCGS Louis S.
St-Laurent to acquire strain gauge data from three locations on the hull: the
bow (24 strain gauges), the shoulder (28 strain gauges) and the bottom (11
strain gauges). To support the load measurements a ship navigation data acquisition and video monitoring system was also installed.
The data acquisition system
was designed to trigger the data
recorder to record significant
impact events when a predetermined load was exceeded. It simultaneously recorded the
speed, power and direction of
the ship, as well as ice thickness
and strength, for later correlation
to ice condition and vessel operations.
The data acquisition system was operational from when the ship entered
the ice on 26 July (70.08°N, 168.38°W) until it exited on 31 August. A total
of 4037 separate events were recorded during that period. Ice observations
were made continuously from the bridge of the Polar Sea. The forward-looking video system recorded the encountered ice, and the after-looking video
system recorded the interaction of broken ice at the location of the strain
gauges. Physical ice data were collected on an opportunity basis by ice science
partners from the Institute of Marine Dynamics, St. John’s, Newfoundland,
to establish the thickness and strength of the encountered ice. The average ice
thickness varied from 1.0 m (3.2 ft) on entry to 2.0 m (6.7 ft) at the Pole. The
maximum ice thickness (excluding ridges) was 3.54 m (11 ft).
The data set derived from this voyage is the largest ever collected on a
single deployment and doubles the quantity of information collected on previous collaborative USCG–CCG projects. The ongoing analysis will reduce
the strain data to pressure loads and assess the trends in data versus ice and
ship operating conditions, compute extreme value statistics and compare results between other areas of this ship and other ship experiments.
Louis S. St-Laurent
breaking ice.
103
1994 Arctic Ocean Section
— Communications and Data Management —
Special Communications Solutions
Michael Powers
The unique environment of the deep Arctic requires special communications solutions, especially with an expedition of the complexity of AOS-94.
Two of the special communications systems developed for and used on AOS94 were the Internet e-mail system and the inter-ship communications system.
Providing Internet e-mail service on polar expeditions poses special problems
as the ship proceeds north of the range of standard geosynchronous communications satellites. Members of the Polar Sea’s communications team explored
a number of options in preparation for the expedition. The solution chosen
was to use the Lincoln Experimental Satellites (LES) to link with the University of Miami ATS Satellite Control Facility at Malabar, Florida.
The two Lincoln Experimental Satellites, LES-8 and LES-9, were developed by MIT’s Lincoln Labs for the Air Force and operate on the military
UHF band (225–400 MHz). Both LESs follow inclined geosynchronous orbits, moving 17.8° north and south of the equator each 24 hours. The Polar
Sea used LES-9 while it was north of the equator, which provided at least four
hours of access each day.
Using the installed Navy Satellite Communications System equipment,
the Polar Sea used data packet technology to send and receive information
with a minicomputer at University of Miami’s site in Malabar, Florida. The
minicomputer provided Internet access for e-mail and file transfer, using the
standard Internet file transfer protocol (ftp).
Aboard the Polar Sea, scientists and crew members prepared outgoing
e-mail as text files on floppy diskettes. E-mail from scientists on the Louis S.
St-Laurent was initially delivered on floppies by helicopter and later by the
inter-ship communications system described below. Incoming e-mail was
printed and delivered to the recipients.
The Internet e-mail connection allowed scientists to communicate with
colleagues ashore throughout the expedition. In one case the ability to communicate by e-mail allowed the scientists and technicians aboard the Polar Sea
to successfully troubleshoot a problem with their equipment. This meant that
they were able to conduct their tests without interruption.
The connection was also used to download ice imagery from the National
Cdr. Michael Powers was Executive Officer of the USCGC Polar Sea.
104
Communications and Data Management
Ice Center. While the Polar Sea’s installed TeraScan system provided real-time
ice imagery, the capability of accessing National Ice Center information provided an option had there been a problem with TeraScan.
For inter-ship communications a VHF-FM line-of-sight link between the
Polar Sea and the Louis S. St-Laurent was installed by Coast Guard technicians
while the expedition was transiting from Victoria, British Columbia, to Nome,
Alaska. This link was tied into each ship’s telephone system, allowing one to pick
up the phone on the Polar Sea and call someone on the Louis S. St-Laurent. This
communications link proved invaluable in allowing the senior leaders of the
expedition on both ships to consult and plan for each day’s operation.
In addition, the link allowed scientists on the Louis S. St-Laurent to send
and receive their e-mail electronically, which was much more reliable than
waiting for the next helicopter flight between the two ships.
105
1994 Arctic Ocean Section
Data Management
Claire S. Hanson and David L. McGinnis
Data from AOS-94 are valuable national and international scientific resources and must be preserved for analysis by both current and future generations of scientists. To ensure preservation, data management coordination for
AOS-94 will be provided by the National Snow and Ice Data Center (NSIDC),
University of Colorado at Boulder. NSIDC is funded by the National Science
Foundation’s Office of Polar Programs as the Data Coordination Center for
the Arctic System Science (ARCSS) Program; the AOS-94 data will be integrated into the ARCSS data management project.
A data archiving plan is being developed in collaboration with the AOS-94
project leaders to ensure that AOS-94 data sets and data products, along with
complete documentation, will be archived at NSIDC and accessible through
discipline-appropriate data centers. Examples of these centers with which
NSIDC has close working relationships include the NOAA National Geophysical Data Center’s Marine Geology and Geophysics Division and its Paleoclimate Group, the NOAA National Oceanographic Data Center, the NOAA
National Climatic Data Center, and the Department of Energy’s Carbon Dioxide Information and Analysis Center. Copies of the marine core data, bathymetric data, physical oceanography and primary productivity data, and atmospheric chemistry and related data from AOS-94 will be sent to these centers
for incorporation into their databases. In cases such as biology and contaminants where there is currently no national center having responsibility for a
particular discipline, NSIDC will maintain that AOS-94 data and provide access services until a discipline center is developed or designated.
NSIDC’s ARCSS Data Coordination Center emphasizes ease of access, comprehensive documentation, and a researcher-centered philosophy. Our goal is
to make the migration of valuable data as easy as possible. For adding data to
the archive we develop a plan with each investigator. When an investigator
and the NSIDC ARCSS staff agree that the data are ready, data sets are transferred to NSIDC and made available via electronic means such as anonymous
ftp and/or the World Wide Web. When logical groupings of data are identified, and the volume is sufficient to warrant it, a CD-ROM is considered as an
Claire Hanson and David McGinnis are with the National Snow and Ice Data Center at the
Cooperative Institute for Research in Environmental Sciences at the University of Colorado in Boulder, Colorado, U.S.A.
106
Communications and Data Management
additional data delivery medium. The ARCSS data management effort is a
two-way street; we work with investigators to archive their data while making
these same data readily available for other investigators.
Data sets and products from AOS-94 will be listed in the on-line and hardcopy versions of the ARCSS Data Catalog, as well as in the Global Change
Master Directory, the Arctic Environmental Data Directory and the International Arctic Environmental Data Directory. These on-line information services provide a means of notifying the international science community of
these data sets, with up-to-date contact information to order the data. In addition, NSIDC maintains an ARCSS Web site (http://arcss.colorado.edu) that
will explicitly list AOS-94 data with ordering information and/or links to download the data from within a Web browser. News of ARCSS data issues and
activities is available in the quarterly newsletter NSIDC Notes, obtainable by
free subscription and on the NSIDC Web site.
The AOS-94 data archiving plan will stipulate a period of exclusive use by
the investigators, perhaps two years from the end of the cruise, after which the
data should be moved into the archive and released for general distribution.
The time period of exclusive use has not yet been negotiated with the project
leaders or the individual investigators.
107
1994 Arctic Ocean Section
— Appendices —
— AOS-94 Participants —
USCGC Polar Sea
Kent Berger-North, Biology
Axys
Sidney, British Columbia
Hazen W. Bosworth, Sea ice
U.S. Army Cold Regions Research and
Engineering Laboratory
Hanover, New Hampshire
Peter C. Brickell, Atmospheric and upper ocean
chemistry
Air Quality Measurements and Analysis
Research Division
Atmospheric Environment Service
Downsview, Ontario
John P. Christensen, Seafloor geochemistry
Bigelow Laboratory for Ocean Sciences
West Boothbay Harbor, Maine
John D. Grovenstein, Atmospheric and upper
ocean chemistry
Department of Marine, Earth and Atmospheric
Sciences
North Carolina State University
Raleigh, North Carolina
Patrick Hart, Marine geology
U.S. Geological Survey
Menlo Park, California
Daniel Lubin, Atmospheric radiation and
climate
California Space Institute
University of California, San Diego
La Jolla, California
Bonnie J. Mace, Biology
Lamont-Doherty Earth Observatory
Palisades, New York
Lisa Clough, Biology
Department of Biology
East Carolina University
Greenville, North Carolina
Steven May, Marine geology
U.S. Geological Survey
Prescott, Washington
Charles Geen, Atmospheric and upper ocean
chemistry
Bovar-Concord Environmental
Toronto, Ontario
Sandy Moore, Biology
College of Oceanic and Atmospheric Sciences
Oregon State University
Corvallis, Oregon
Michel Gosselin, Biology
Department of Oceanography
University of Quebec at Rimouski
Rimouski, Quebec
Michael Mullen, Marine geology
U.S. Geological Survey
Menlo Park, California
Anthony J. Gow, Sea ice
U.S. Army Cold Regions Research and
Engineering Laboratory
Hanover, New Hampshire
Arthur Grantz, Marine geology
U.S. Geological Survey
Menlo Park, California
108
Mary O’Brien, Biology
Institute of Ocean Sciences
Sidney, British Columbia
Walter Olson, Marine geology
U.S. Geological Survey
Menlo Park, Californi
Elizabeth Osborne, Marine geology
McLean Laboratory
Woods Hole Oceanographic Institution
Woods Hole, Massachusetts
AOS-94 Participants
Kevin O’Toole, Marine geology
U.S. Geological Survey
Menlo Park, California
Fred Payne, Marine geology
U.S. Geological Survey
Menlo Park, California
Larry Phillips, Marine geology
U.S. Geological Survey
Menlo Park, California
Erk Reimnitz, Sea ice
U.S. Geological Survey
Menlo Park, California
James Rich, Biology
Graduate College of Marine Studies
University of Delaware
Lewes, Delaware
William Robinson, Marine geology
U.S. Geological Survey
Menlo Park, California
Larry Schultz, Ship technology
Advanced Marine Enterprises
Arlington, Virginia
Rubin Sheinberg, Ship technology
Naval Engineering Division
U.S. Coast Guard
Baltimore, Maryland
Evelyn Sherr, Biology
College of Oceanic and Atmospheric Sciences
Oregon State University
Corvallis, Oregon
Nathalie Simard, Biology
Department of Oceanography
University of Quebec at Rimouski
Rimouski, Quebec
Delphine Thibault, Biology
Department of Oceanography
University of Quebec at Rimouski
Rimouski, Quebec
Walter Tucker, Sea ice
U.S. Army Cold Regions Research and
Engineering Laboratory
Hanover, New Hampshire
Patricia Wheeler, Biology
College of Oceanic and Atmospheric
Sciences
Oregon State University
Corvallis, Oregon
Robert A. Whritner, Atmospheric radiation and
climate
Arctic and Antarctic Research Center
Scripps Institution of Oceanography
University of California, San Diego
La Jolla, California
Louis S. St-Laurent
Knut Aagaard, Oceanography
Applied Physics Laboratory
University of Washington
Seattle, Washington
Louise Adamson, Contaminants
Institute of Ocean Sciences
Sidney, British Columbia
Ikaksak Amagoalik, Oceanography
Institute of Ocean Sciences
Sidney, British Columbia
Ken Asmus, Sea ice and remote sensing
Ice Services Branch
Atmospheric Environment Service
Ottawa, Ontario
Janet E. Barwell-Clarke, Oceanography
Institute of Ocean Sciences
Sidney, British Columbia
Eddy Carmack, Oceanography
Institute of Ocean Sciences
Sidney, British Columbia
Sylvester Drabitt, Documentation
Institute of Ocean Sciences
Sidney, British Columbia
Brenda Ekwurzel, Oceanography
Lamont-Dougherty Earth Observatory
Palisades, New York
James A. Elliott, Oceanography
Bedford Institute of Oceanography
Dartmouth, Nova Scotia
Katherine Ellis, Contaminants
Bedford Institute of Oceanography
Dartmouth, Nova Scotia
109
1994 Arctic Ocean Section
Sean Farley, Marine mammals
Department of Zoology
Washington State University
Pullman, Washington
Caren Garrity, Sea ice and remote sensing
Microwave Group-Ottawa River
Dunrobin, Ontario
Wayne Grady, Documentation
Macfarlane, Walter and Ross
Toronto, Ontario
Michael Hingston, Oceanography
BDR Research Ltd
Bedford Institute of Oceanography
Dartmouth, Nova Scotia
Rick Pearson, Oceanography
Institute of Ocean Sciences
Sidney, British Columbia
Ron Perkin, Oceanography
Institute of Ocean Sciences
Sidney, British Columbia
Malcolm Ramsay, Marine mammals
Department of Biology
University of Saskatchewan
Saskatoon, Saskatchewan
Ron Ritch, Ship technology
A.R. Engineering
Calgary, Alberta
Oolateetah Iqaluk, Oceanography
Institute of Ocean Sciences
Sidney, British Columbia
James A. Schmitt, Oceanography
Scripps Institution of Oceanography
University of California, San Diego
La Jolla, California
Liisa M. Jantunen, Contaminants
Atmospheric Environment Service
Downsview, Ontario
Douglas Sieberg, Oceanography
Institute of Ocean Sciences
Sidney, British Columbia
E. Peter Jones, Oceanography
Bedford Institute of Oceanography
Dartmouth, Nova Scotia
James St. John, Ship technology
Science and Technology Engineering Corporation
Columbia, Maryland
Robie Macdonald, Contaminants
Institute of Ocean Sciences
Sidney, British Columbia
James H. Swift, Oceanography
Scripps Institution of Oceanography
University of California, San Diego
La Jolla, California
Fiona McLaughlin, Oceanography/contaminants
Institute of Ocean Sciences
Sidney, British Columbia
Christopher Measures, Oceanography
Department of Oceanography
University of Hawaii
Honolulu, Hawaii
Darren Tuele, Contaminants
Institute of Ocean Sciences
Sidney, British Columbia
Christopher Walker, Documentation
Institute of Ocean Sciences
Sidney, British Columbia
David A. Muus, Oceanography
Scripps Institution of Oceanography
University of California, San Diego
La Jolla, California
Robert T. Williams, Oceanography
Scripps Institution of Oceanography
University of California, San Diego
La Jolla, California
Richard Nelson, Contaminants
Bedford Institute of Oceanography
Dartmouth, Nova Scotia
F. Mary Williams, Sea ice
NRC Institute for Marine Dynamics
St. John’s, Newfoundland
Stefan Nitoslawski, Documentation
Galafilm, Inc.
Montreal, Quebec
Frank Zemlyak, Oceanography
Bedford Institute of Oceanography
Dartmouth, Nova Scotia
David Paton, Contaminants
Institute of Ocean Sciences
Sidney, British Columbia
110
AOS-94 Participants
CCGS Louis S. St-Laurent Crew
Commanding Officer
Chief Officer
First Officer
Second Officer
Third Officer
Bosun
Carpenter
Leading Seaman
Leading Seaman
Leading Seaman
Seaman
Seaman
Seaman
Seaman
Seaman
Seaman
Philip Grandy
Michael Hemeon
William Turner
Stephen Baxter
Thomas Lafford
Abraham Welcher
Phillip Walker
Dale Hiltz
Leslie Drake
Kenneth Baker
Rico Amamio
Alfred Jarvis
Albert Sears
Karl Gouthro
William Wallace
Arthur Larkin
Logistics Officer
Logistics Officer
Chief Cook
Senior Storekeeper
Storekeeper
Clerk
Cook
Cook
Steward
Steward
Steward
Steward
Steward
Steward
Steward
Steward
Steward
James Purdy
Elizabeth Campbell
Randy Turner
David Wallingham
Rick Strickland
Angela Macdonald
Stephen Oliver
Daneil Jones
Graham Weldon
Graham Ritchie
Graeme Garrett
Jacqueline Bourdon
Leo Higgins
Ralph Bowley
Mark Lewis
Robert Schoots
Thomas Beaver
Chief Engineer
Sr Electrical Officer
Jr Electrical Officer
Senior Engineer
First Engineer
Second Engineer
Third Engineer
Supernumery Engineer
Electrician
Electrician
Engineroom Supervisor
Engineroom Technician
Engineroom Technician
Engineroom Technician
Engineroom Technician
Oiler
Oiler
Oiler
Oiler
Oiler
Oiler
Oiler
Mark Cusack
Phillip Seaboyer
William Falconer
Nigel Hawksworth
Mark Frogley
Matthew Turner
David Baker
Darrin Arkerman
Chris Wood
Edward Ginter
David Baur
Wayne Ryan
Kenneth Pettipas
Stephen Baxter
William Fagan
Phil Macpherson
Robert Boucher
Greg Engler
Thomas Hann
Stephen Gagnon
Winston Langille
Alexander Myers
Radio Operator
Electronics Technician
Ice Observer
Helicopter Pilot
Helicopter Pilot
Helicopter Engineer
Nurse
Gordon Stoodley
Robert Brown
Alfred Kooz
Yvan Giroux
Ralph Hemphill
Percy Gammon
Cylethia Lee
USCGC Polar Sea Crew
Officers
CAPT Lawson W. Brigham
CDR Michael N. Powers
LCDR Daniel K. Oliver
LCDR Robert L. Kaylor
LCDR Stephen M. Wheeler
LCDR Steven G. Sawhill
LT Edward J. Hansen
LT Kevin M. Balderson
LT Theodore R. Salmon
LT April A. Brown
LTJG Karen Arnold
LTJG Lawrence C. Goerss
LTJG Edward J. Lane III
LTJG John D. Reeves
ENS Vincent J. Skwarek
Commanding Officer
Executive Officer
Engineering Officer
Senior Aviation Officer
Deck Watch Officer/Ice Pilot
Operations Officer
Aviation Engineering Officer
Aviation Operations Officer
Aviation Administration Officer
Deck Watch Officer/Marine Science Officer
Deck Watch Officer/Exchange Officer
Damage Control Assistant/Morale Officer
Deck Watch Officer/Communications Officer
Assistant Engineering Officer
Student Engineer
111
1994 Arctic Ocean Section
ENS Sean M. Carroll
CW04 Charles R. Steele, Jr.
CW04 James J. Levesque
CW03 Donald A. Knesebeck
CW02 Harry J. Poland
CW02 James E. Carlin
Enlisted Personnel
EMCM Warren E. Booth
EMC Jann H. Millard
EMC Carl D. Pieplow
EM2 Robert T. Nietering
EM2 Gerard A. Hebert Jr.
EM2 Charles G. McPhee
EM3 Terry L. Maurer Jr.
EM3 Oscar O. Beck
EM3 Clinton S. Thurlow
ETCS Peter W. Churchill
ETC Robert J. Reiter
ET1 Johnny N. Allen
ET3 Randall C. Kibler
ET3 Cary D. Biss
ET3 Todd A. Grant
ET3 Stuart D. Robertson II
TT2 James E. Riley
FN Barbara C. Bennett
FN Larry W. Bishop
FN Eric F. Cheigh
FN Patrick J. Corso
FN Daniel R. Ferguson
FN John R. Hays
FN Stephen L. McVay
QMCM Gary A. Thurston
QM2 Gil A. Contreras
QM3 Jennifer M. Hogge
QM3 Peter J. Kanavas
QM3 Laura L. Knehr
BMCS Charles D. Buckley
BM1 Christopher R. Buell
BM2 Anthony D. Whiting
BM3 Hans Esteves
112
Deck Watch Officer/Administrative Officer
Supply Officer
Engineering Watch/Electronics Officer
Deck Watch Officer/First Lieutenant
Medical Officer
Engineering Watch/Main Propulsion Asst.
DCC Michael W. Andreucci
DC2 Michael J. McAndrews
DC2 Ronald C. Plowman
DC3 David C. Garner
MKCM Jeffery J. Andrie
MKC Glenn J. West
MKC Troy T. Luna
MK1 Daniel L. Lenz
MK1 Garry D. Bennett
MK1 Donald S. Nothem
MK1 Marvin L. Heeter Jr.
MK2 Thomas L. Dammann
MK2 James E. Hale II
MK3 Eric C. Alfred
MK3 Juan C. Juarez
MK3 Raymond A. Morris III
MK3 Jeffrey R. Siron
MK3 Jason T. Watkins
FN Richard E. Russell
FN Patrick J. Vincler
FA Louis E. Frattarelli Jr.
FA Sean P. McSweeney
FA Jeffrey P. Pierce
FA Maurice Ponce
FA Thomas J. Scheidemantel
YNC Terrence J. Brennan
YN1 Langston D. Brooks
YN2 Brian P. McClure
SKC Dana V. Hanberg
SK2 Robert T. King
SK1 Bryan D. Petersen
SK3 Michael B. Sanicharra
SN Joseph A. Bergman
GM1 Vincent L. Demeyer
HSC Mark L. Stocks
HS2 Jeffrey W. Ongemach
SN Mitchel H. Barker
SN Jason M. Crandall
SN Derrick L. Cross
SN Adam P. High
SN Loren D. Huggins
SN Peter M. Jagel
SN Robert J. Odaniel
SN Andy R. Stafford
SN Jason A. Stouffer
SN Bradley R. Tull
SA Jakobb N. Baldwin
SA Lura D. Etchison
AOS-94 Participants
SN Sean M. Johannsen
SN Justin R. Jolley
SN Matthew M. Kenny
SN Cobran D. Lappin
SN Wesley McMillan III
SN James A. McMurphy
SA David B. Gore
SA Matthew E. Kor
SA Jason T. Lopez
SA Collin A. Maas
SA Aaron S. Schmude
SA Jeffrey E. Williams
MST1 Corey A. Bennett
MST2 John T. Pierce
MST3 Noell A. Bolleurs
MST3 Elisa M. Fusco
RM1 Steven M. Schofield
RM2 Matthew J. Dini
RM2 Paul J. Gladding
RM2 Jeffrey D. Spears
RM3 Scott D. Haywood
RM3 Rod E. Koepp
SSCS Alan R. Walsh
SS1 Michael T. Lapolla
SS1 Michael R. Sieg
SS1 Joseph Grant
SS2 Nathaniel Hightower
SS3 Douglas A. Van Kampen
SS3 Jonathan R. Carton
SS3 Jimmie L. Patterson
SS3 Ruston C. Johnson
SNSS Kenneth J. Bennett
ADC Robert C. Fawcett
AD1 William D. Anderson
AE1 Mark R. Mobley
AT1 Scott W. Thiel
AD2 Michael B. Kellams
AT2 Henry C. Parker
AE2 William J. Shaw
AM3 J. Guillermo Verde
113
1994 Arctic Ocean Section
— Science Stations —
Polar Sea
No.
Date
N Lat.
Long.
Depth (m)
1
2
3
4
5
6
7
7b
8
8a
9
10
11
12
13
13a
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
25 Jul
26 Jul
27 Jul
28 Jul
30 Jul
30 Jul
1 Aug
2 Aug
3 Aug
3 Aug
4 Aug
4 Aug
4 Aug
5 Aug
6 Aug
6 Aug
7 Aug
7 Aug
8 Aug
9 Aug
10 Aug
11 Aug
12 Aug
13 Aug
14 Aug
15 Aug
16 Aug
18 Aug
19 Aug
19 Aug
19 Aug
20 Aug
20 Aug
22 Aug
25 Aug
26 Aug
67°59′
70°00′
72°00′
74°01′
75°25′
75°21′
76°39′
77°49′
78°08′
78°09′
78°08′
78°09′
78°58′
79°59′
80°09′
80°09′
80°13′
80°12′
80°20′
81°15′
81°34′
82°26′
83°10′
84°06′
84°50′
85°54′
87°09′
88°04′
88°48′
88°52′
88°52′
88°56′
89°01′
89°59′
85°43′
84°16′
168°50′W
168°45′W
168°51′W
168°50′W
170°44′W
170°30′W
173°20′W
176°21′W
176°48′W
176°02′W
176°41′W
174°38′W
175°48′W
174°17′W
173°17′W
173°22′W
172°46′W
173°19′W
178°43′W
179°00′E
176°58′E
175°50′E
174°06′E
174°59′E
170°42′E
166°50′E
160°32′E
147°47′E
143°29′E
141°55′E
140°31′E
138°55′E
137°41′E
031°45′E
037°50′E
034°37′E
49
40
55
120
900
525
2250
1047
1426
1035
1673
1050
1638
2654
2556
3098
2726
1568
2255
2414
3145
3205
3535
4020
2191
1034
1634
2015
3047
4064
4290
3585
4052
*P-production, B-biomass, Bc-box core, Pc-piston core, I-ice.
114
Sampling program*
Bc
P, B, Bc (5), I
P, B, I
P, B, I
P, B, I
B, Bc (2)
P, B, Bc (2), I
I
P, B, Bc (2), Pc, I
Pc
Pc
Pc
B
B, Bc, Pc (2), I
P, B, Pc
Bc, I
Pc
Pc
B, Bc (3), Pc, I
P, B, Bc (2), I
I
P, B, Bc (2), I
Bc, Pc, I
P, B, Bc, Pc, I
I
P, B, Bc (2), I
P, B, Bc, Pc
P, B, Bc (2), I
B, Bc (2)
Pc
Bc, Pc, I
Bc, Pc
Bc, I
P (2), B (2), Bc, Pc, I
P, B, Bc (2), I
P, B, Bc, I
Science Stations
Combined P and B stations include CTD, nutrients, pCO2, halocarbons,
organics, DMSP, DOC, DON, POC, PON, zooplankton, chlorophyll, phytoplankton, heterotrophic protists, bacteria, primary production, nutrient uptake, bacterial production, protistan herbivory, bactivory, zooplankton excretion, and zooplankton herbivory.
B stations include CTD, nutrients, halocarbons, and chlorophyll.
Box cores (Bc) were variously sampled depending on whether they served
the geological or biological programs.
I stations include ice cores, albedo, sediments, and ice contaminants.
Depths are uncorrected.
In addition, over 1300 nautical miles of video and still photography ice
morphology survey lines were flown to measure floe and melt pond size distributions.
Atmospheric chemistry and physics measurements were made throughout
the voyage, either continuously or through flask sampling or intermittent
pumping. These observations include volatile organics, dimethyl sulfide, ozone,
carbon monoxide and dioxide, organohalides, sulfur dioxide and acid gases,
major ions and stable isotopes, aerosols and condensation nuclei. Measurements of halomethanes in water, snow and ice were made while on station.
Radiation measurements were also made throughout the voyage. These
were done with a Fourier transform IR spectroradiometer (mid-IR), an experimental near-IR detector, a total IR pyrgeometer, a solar pyranometer, a nearIR pyranometer and a UV radiometer.
115
1994 Arctic Ocean Section
Louis S. St-Laurent
No.
Date
N Lat.
Long.
Depth (m)
Sampling program *
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
25 Jul
27 Jul
28 Jul
28 Jul
28 Jul
29 Jul
29 Jul
29 Jul
30 Jul
30 Jul
1 Aug
2 Aug
2 Aug
3 Aug
4 Aug
4 Aug
5 Aug
6 Aug
7 Aug
8 Aug
8 Aug
9 Aug
9 Aug
10 Aug
11 Aug
12 Aug
13 Aug
15 Aug
16 Aug
18 Aug
19 Aug
19 Aug
20 Aug
20 Aug
22 Aug
25 Aug
26 Aug
27 Aug
31 Aug
67°47′
72°08′
73°00′
73°30′
73°59′
74°30′
75°00′
75°27′
75°45′
75°57′
76°38′
77°20′
77°48′
78°09′
78°08′
78°59′
79°59′
80°09′
80°09′
80°20′
80°43′
81°15′
81°35′
82°28′
83°10′
84°04′
84°51′
85°54′
87°09′
88°04′
88°47′
88°52′
88°57′
89°01′
90°00′
85°44′
84°15′
83°51′
75°00′
168°47′W
168°50′W
168°49′W
168°51′W
168°44′W
168°50′W
169°59′W
170°35′W
171°14′W
171°40′W
173°19′W
175°02′W
176°18′W
176°54′W
174°18′W
175°49′W
174°19′W
173°15′W
176°46′W
178°38′W
179°59′W
179°01′E
176°52′E
175°40′E
173°56′E
175°04′E
170°42′E
166°42′E
160°42′E
147°50′E
142°44′E
140°00′E
139°12′E
137°09′E
50
53
66
116
184
195
261
887
1679
1886
2227
1852
1217
956
1853
1062
1670
2655
2115
1436
1640
2208
2524
2430
3088
3135
3323
3456
3939
2130
1029
1983
2938
4080
4215
3471
3979
3954
3448
O, C
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O, I
O, C, I
O, I
O, C, I
O, C, I
O, I
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O, C, I
O
O, C
37°45′E
35°05′E
35°41′E
6°03′W
*O-oceanography, C-contaminants, I-ice.
116
Science Stations
O stations include CTD, oxygen, nutrients, carbonate and alkalinity, CFCs
(including CC14, helium-tritium, 18O, 14C and trace metals.
C stations include hydrocarbons, HCHs, other organics (e.g., toxophenes),
radionuclides and trace metals, using both large-volume bottle sampling and
submerged and surface pumps. Contaminant samples were also collected from
snow samples, net hauls and box cores.
I stations variously include vertical temperature and salinity profiles in the
ice, beam tests, crystallography, and electrical and physical properties of the
snow cover. There were also continuous ship-based radiation measurements at
37 GHz, vertically polarized.
Depths are uncorrected.
In addition, 72 CTD stations to 1500 m were occupied using a portable
system carried by helicopter and deployed from the ice. Two 48-hr contaminant moorings were also deployed and recovered by helicopter. Finally, the marine
mammals program made detailed studies of seven polar bears, again working
from helicopters.
117
1994 Arctic Ocean Section
1994 ARCTIC OCEAN SECTION
0
200
1000 2000 3000
DEPTH (meters)
4000
5000
Cruise track of the Louis S. St-Laurent and the Polar Sea between July 24 and September 3, 1994.
The dots represent the science stations. (Map created by Christopher Guay.)
Ship and helicopter photos on previous page by Peter Brickell.
1994 Arctic Ocean Section
90–100%
70–80%
DMSP SSMI 85GHZ
15 Aug 94 2325Z
Total Ice Cont.
45–55%
20–30%
0–3%
Total ice concentration for August 15, 1994. The track of the Polar Sea is shown in white. This
Defense Meteorological Satellite Program (DMSP ) image was derived using the 85-GHz passive
microwave channel of the Special Sensor Microwave Imager (SSM/I). The images were received
and processed in near real time by the TeraScan system aboard the Polar Sea. For more information
about how images such as this were created and used during AOS-94, see p. 97.
Photo on back cover by Charles Geen